DOCSLIB.ORG

The Linker of Des-Glu84-Calmodulin Is Bent (Calcium/Mutagenesis/Flexible Tether/Bent A-Helix/Crystallography) S

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Linker of Des-Glu84-Calmodulin Is Bent (Calcium/Mutagenesis/Flexible Tether/Bent A-Helix/Crystallography) S Proc. Natl. Acad. Sci. USA Vol. 90, pp. 6869-6873, July 1993 Biochemistry The linker of des-Glu84-calmodulin is bent (calcium/mutagenesis/flexible tether/bent a-helix/crystallography) S. RAGHUNATHAN*, R. J. CHANDROSSt, B.-P. CHENG*t, A. PERSECHINI*§, S. E. SOBOTTKAt, AND R. H. KRETSINGER* Departments of *Biology and tPhysics, University of Virginia, Charlottesville, VA 22901 Communicated by William N. Lipscomb, April 1, 1993 ABSTRACT The crystal structure of a mutant calmodulin 111111111122 22222222 (CaM) lacking Glu-84 has been refined to R = 0.23 using data 123456789 012345678901 23456789 measured to 2.9-A resolution. In native CaM the central helix domain n nn n X Y Z(Y) X Z n nn n is fully extended, and the molecule is dumbbell shaped. In contrast, the deletion of Glu-84 causes a bend of 950 in the 1 ADQLTEEQIA EFKEAFSLF DKDGDGTITTKE LGTVMRSL39 linker region of the central helix at Ile-85. However, EF-hand 2 GQNPTEA ELQDMINEV DADGNGTIDrPz rLTMKARKP75 domains 1 and 2 (lobe 1,2) do not touch lobe 3,4. The length, by a-carbon separation, of des-Glu5"-CaM is 56 A; that of 3 76MKDTDSEE EIRZAFRVr DKDGNGYISAAE LRHVMTNL112 native CaM is 64 A. The shape of des-Glu"-CaM is similar to 4 GEKLTDE EVDEMIREA DIDGDGQVNYEE FVQMMTAK148 that ofnative CaM, as it is bound to the target peptide ofmyosin light-chain kinase. This result supports the proposal that the FIG. 1. The amino acid sequence ofvertebrate CaM is aligned by linker region of the central helix of CaM functions as a flexible its four EF-hand domains, each consisting of 29 residues. The side tether. chains whose oxygen atoms coordinate calcium are aligned under X, Y, Z, -X, -Z. The carbonyl oxygen of (-Y) coordinates calcium with its peptide oxygen. The insides ofa-helices E and F usually have Calmodulin (CaM) is the most extensively studied of the 30 hydrophobic side chains, indicated by n. The central helix consists subfamilies (1) that contain two to eight EF-hand domains. It of the second (F) helix of domain 2, the eight-residue linker 76-83, regulates numerous target enzymes and structural proteins and the first (E) helix ofdomain 3. Glu-84, the first residue ofdomain (2) and is inferred to be present in all cells of all eukaryotes. 3, is shown in italics as the residue deleted in des-Glu4-CaM. The We want to understand the mechanisms whereby CaM trans- region Lys-77-Thr-79 is predicted not to be helical. Native CaM with duces the information in a pulse of Ca2+ ions in the cytosol three glutamates has a slightly stronger helix-forming tendency than to a change of conformation of a target enzyme. To this end does des-Glu84-CaM with only two adjacent glutamates. There is a Persechini and Kretsinger (3) made three mutant CaMs in bend of 950 in the helix centered about Ile-85 and a bend of 40' at which the linker region of the central helix has one (des- Lys-75 in des-Glu"-CaM. Glu84-CaM), two (des-Glu83, Glu4-CaM), or four (des-Ser8l, range 3.1-2.9 A the redundancy is 2.1, the mean I/ar is 5.3, Glu82, Glu83, Glu84-CaM) residues deleted. Persechini et al. and the scaling residual is 0.115. (4) treated mutated CaM (Gln-3 -3 Cys, Thr-146 -) Cys) with bismaleimidohexane to cross-link this mutated CaM into a Given the difficulty of growing larger crystals and the bent form. On the basis ofthe abilities ofthese deletion CaMs assumed similarity in structure of native CaM and of des- to activate skeletal muscle myosin light-chain kinase Glu84-CaM, we computed self-rotation and molecular replace- (skMLCK), NAD kinase, and calcineurin (protein phospha- ment functions. We routinely describe the EF-hand domain in tase) and of the cross-linked CaM to activate skMLCK, they terms of 29 residues, as illustrated in Fig. 1 and explained in proposed "that the central helix of calmodulin functions as a its legend. The four canonical domains of CaM extend from flexible tether." residue 11 through 39, 47-75, 84-112, and 120-148. We anticipated that des-Glu84-CaM would have four EF-hand EXPERIMENTAL PROCEDURES domains with domains 1 and 2 related by an approximate 2-fold Des-Glu4-CaM was prepared, as described by Persechini rotation axis forming lobe 1,2, very similar to those observed and Kretsinger (3), and was crystallized by vapor distillation in native CaM and troponin C (TnC). Lobe 3,4 should also from drops over reservoirs of 20%o saturated ammonium consist ofa pair of EF-hands related by an approximate 2-fold sulfate/10 mM CaCl2/50 mM 2-(N-morpholino)ethanesulfo- rotation axis. We hoped to determine the rotation operation nic acid, pH 6.1, at both 4°C and 20'C. Initial drops consisted relating lobe 1,2 to lobe 3,4. We found a single rotation axis in of 8.0 ,ul of des-Glu84-CaM at 10 mg/ml and 8.0 ,ul of the self-rotation function with the rotation value K 1800. We reservoir. Our largest crystals seldom exceeded 0.25 mm in could interpret this result only in terms of the subsequent any dimension; diffraction was weak beyond 2.9 A. Unit cell molecular replacement calculations. dimensions and intensity data were measured at the Multi- Molecular replacement searches were computed by using wire Area X-ray Diffractometer Facility (5). Systematic the package CCP4 (6). We used lobe 1,2 (residues 11-75) and absences indicate space group P212121 with unit cell dimen- lobe 3,4 (84-147) as probes (probe 1,2 and probe 3,4). The sions a = 45.3, b = 49.9, c = 62.4 A; one molecule per results were relatively insensitive to the exact definition of asymmetric unit. The 3396 unique reflections of 3483 avail- probe termini as well as to both radius of integration and able reciprocal lattice points were measured to a resolution of resolution of data used. On the basis of several preliminary 2.9 A. The redundancy ofmeasurements is 3.8. The mean I/oa trials we used 20-A radius, 10- to 4-A data, and all nonhy- is 6.6; 2371 reflections have I/cr > 3.0. The overall scaling residual - I,I/n is 0.09. In the resolution Abbreviations: CaM, calmodulin; TnC, troponin C; skMLCK, skel- Y:.=j[7,jgi(Iji Ijj)/m etal muscle myosin light-chain kinase. *Present address: Institute of Solid State Physics, Academia Sinica, The publication costs of this article were defrayed in part by page charge Hefei, People's Republic of China. payment. This article must therefore be hereby marked "advertisement" §Present address: Department of Physiology, School of Medicine, in accordance with 18 U.S.C. §1734 solely to indicate this fact. University of Rochester, Rochester, NY 14642. 6869 Downloaded by guest on September 26, 2021 6870 Biochemistry: Raghunathan et al. Proc. Natl. Acad Sci. USA 90 (1993) drogen atoms. In cross-rotation functions probe 1,2 gave rotation peaks). As anticipated, the resulting maps were very three significant peaks (Fig. 2A), and probe 3,4 gave two of noisy because each search used only halfofthe molecule. We the three (Fig. 2B). Similar results were obtained when atoms then used each of several solutions to the translation function beyond the (3-carbon were omitted, the polyalanine model. for probe 1,2 as a fixed contribution, while we searched for Because the two lobes of CaM are so similar, it was expected the translation component of probe 3,4 and vice versa. We that both probes would give the same two peaks, one found only one rotation, translation solution for probe 1,2 corresponding to the 1,2 lobe of des-Glu84-CaM and one that gave a significant solution for probe 3,4 and conversely corresponding to lobe 3,4. We could not, however, at this only one rotation, translation solution for probe 3,4 that gave point determine which search peak corresponded to which a significant solution for probe 1,2 (Fig. 2 C and D). lobe of des-Glu4-CaM. At this point we had tentatively identified the correct We computed translation functions for both cross-rotation rotation and translation matrices for probe 1,2 and for probe function solutions (and as a control for several smaller 3,4 but did not know which corresponded to lobe 1,2 of A CROSS ROT PROBE 1,2 B CROSS ROT PROBE 3,4 -6C 1800 0 I~~so at 180 JR 7 360 360 a = 75, 80, 85 & 90 = 85&90 C D ci; tOSS TRANS FIX 3,4 PROBE 1,2 CROSS TRANS FIX 1,2 PROBE 3,4 ' Z 0.5 0 Z 0.5 v X --I= ocr 0.5 0.5 Y = 0.214, 0.228, 0.242, 0.256 & 0.270 Y = 0.343, 0.357, 0.371 & 0.385 FIG. 2. Molecular replacement calculations using both lobe 1,2 and lobe 3,4 ofnative CaM as probes revealed the orientations and translations of the two lobes of des-Glu84-CaM. The radius of integration is 20 A; data from 10-4 A are used. (A) Cross-rotation (CROSS ROT) function computed including all side chains of residues 11-75 (lobe 1,2) of native CaM as probe. The map is computed at 19 intervals of , from 00 through 900. Contours are drawn at 3.6 times the mean level, exclusive of the origin peak, and are displayed, in superposition, for levels i3 = 750, 800, 850, and 900.
Load more

Recommended publications
  • Back-To-Basics: the Intricacies of Muscle Contraction
    Back-to- MIOTA Basics: The CONFERENCE OCTOBER 11, Intricacies 2019 CHERI RAMIREZ, MS, of Muscle OTRL Contraction OBJECTIVES: 1.Review the anatomical structure of a skeletal muscle. 2.Review and understand the process and relationship between skeletal muscle contraction with the vital components of the nervous system, endocrine system, and skeletal system. 3.Review the basic similarities and differences between skeletal muscle tissue, smooth muscle tissue, and cardiac muscle tissue. 4.Review the names, locations, origins, and insertions of the skeletal muscles found in the human body. 5.Apply the information learned to enhance clinical practice and understanding of the intricacies and complexity of the skeletal muscle system. 6.Apply the information learned to further educate clients on the importance of skeletal muscle movement, posture, and coordination in the process of rehabilitation, healing, and functional return. 1. Epithelial Four Basic Tissue Categories 2. Muscle 3. Nervous 4. Connective A. Loose Connective B. Bone C. Cartilage D. Blood Introduction There are 3 types of muscle tissue in the muscular system: . Skeletal muscle: Attached to bones of skeleton. Voluntary. Striated. Tubular shape. Cardiac muscle: Makes up most of the wall of the heart. Involuntary. Striated with intercalated discs. Branched shape. Smooth muscle: Found in walls of internal organs and walls of vascular system. Involuntary. Non-striated. Spindle shape. 4 Structure of a Skeletal Muscle Skeletal Muscles: Skeletal muscles are composed of: • Skeletal muscle tissue • Nervous tissue • Blood • Connective tissues 5 Connective Tissue Coverings Connective tissue coverings over skeletal muscles: .Fascia .Tendons .Aponeuroses 6 Fascia: Definition: Layers of dense connective tissue that separates muscle from adjacent muscles, by surrounding each muscle belly.
    [Show full text]
  • Muscle Physiology Dr
    Muscle Physiology Dr. Ebneshahidi Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Skeletal Muscle Figure 9.2 (a) Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Functions of the muscular system . 1. Locomotion . 2. Vasoconstriction and vasodilatation- constriction and dilation of blood vessel Walls are the results of smooth muscle contraction. 3. Peristalsis – wavelike motion along the digestive tract is produced by the Smooth muscle. 4. Cardiac motion . 5. Posture maintenance- contraction of skeletal muscles maintains body posture and muscle tone. 6. Heat generation – about 75% of ATP energy used in muscle contraction is released as heat. Copyright. © 2004 Pearson Education, Inc., publishing as Benjamin Cummings . Striation: only present in skeletal and cardiac muscles. Absent in smooth muscle. Nucleus: smooth and cardiac muscles are uninculcated (one nucleus per cell), skeletal muscle is multinucleated (several nuclei per cell ). Transverse tubule ( T tubule ): well developed in skeletal and cardiac muscles to transport calcium. Absent in smooth muscle. Intercalated disk: specialized intercellular junction that only occurs in cardiac muscle. Control: skeletal muscle is always under voluntary control‚ with some exceptions ( the tongue and pili arrector muscles in the dermis). smooth and cardiac muscles are under involuntary control. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Innervation: motor unit . a) a motor nerve and a myofibril from a neuromuscular junction where gap (called synapse) occurs between the two structures. at the end of motor nerve‚ neurotransmitter (i.e. acetylcholine) is stored in synaptic vesicles which will release the neurotransmitter using exocytosis upon the stimulation of a nerve impulse. Across the synapse the surface the of myofibril contains receptors that can bind with the neurotransmitter.
    [Show full text]
  • Titin N2A Domain and Its Interactions at the Sarcomere
    International Journal of Molecular Sciences Review Titin N2A Domain and Its Interactions at the Sarcomere Adeleye O. Adewale and Young-Hoon Ahn * Department of Chemistry, Wayne State University, Detroit, MI 48202, USA; [email protected] * Correspondence: [email protected]; Tel.: +1-(313)-577-1384 Abstract: Titin is a giant protein in the sarcomere that plays an essential role in muscle contraction with actin and myosin filaments. However, its utility goes beyond mechanical functions, extending to versatile and complex roles in sarcomere organization and maintenance, passive force, mechanosens- ing, and signaling. Titin’s multiple functions are in part attributed to its large size and modular structures that interact with a myriad of protein partners. Among titin’s domains, the N2A element is one of titin’s unique segments that contributes to titin’s functions in compliance, contraction, structural stability, and signaling via protein–protein interactions with actin filament, chaperones, stress-sensing proteins, and proteases. Considering the significance of N2A, this review highlights structural conformations of N2A, its predisposition for protein–protein interactions, and its multiple interacting protein partners that allow the modulation of titin’s biological effects. Lastly, the nature of N2A for interactions with chaperones and proteases is included, presenting it as an important node that impacts titin’s structural and functional integrity. Keywords: titin; N2A domain; protein–protein interaction 1. Introduction Citation: Adewale, A.O.; Ahn, Y.-H. The complexity of striated muscle is defined by the intricate organization of its com- Titin N2A Domain and Its ponents [1]. The involuntary cardiac and voluntary skeletal muscles are the primary types Interactions at the Sarcomere.
    [Show full text]
  • Muscular System ANS 215 Physiology and Anatomy of Domesticated Animals
    Muscular System ANS 215 Physiology and Anatomy of Domesticated Animals I. Skeletal Muscle Contraction A. Neuromuscular junction functions as an amplifier for a nerve impulse B. Arrival of a spinal or cranial nerve impulse at the neuromuscular junction results in release of acetylcholine (Ach) into the space between the nerve fiber terminal branch and the muscle fiber C. Release of Ach is accelerated because Ca ions from extracellular fluid enter the prejunctional membrane when the nerve impulse arrives D. Ach is the stimulus that increases the permeability of the muscle fiber membrane for Na ions, after which depolarization begins E. Depolarization proceeds in all directions from the neuromuscular junction F. Impulse is conducted into all parts of the muscle fiber by the sarcotubular system (synchronizes muscle fiber contraction) G. Low concentration of Ca in the extracellular fluid is recognized clinically in dairy cows after calving (parturient paresis) as a state of semi-paralysis caused by partial neuromuscular block. H. Almost immediately after its release Ach is hydrolyzed by the enzyme acetylcholinesterase into acetic acid and choline I. Next depolarization must await the arrival of the next nerve impulse J. Tubules of sarcoplasmic reticulum have a relatively high concentration of Ca ions K. Depolarization of these tubules results in a simultaneous release of Ca ions into the sarcoplasm, which in turn diffuse rapidly into the myofibrils L. Presence of Ca ions within the myofibrils initiates the contraction process M. The Ca ions are returned rapidly by active transport to the sarcoplasmic reticulum after contraction is initiated and are released again when the next signal arrives.
    [Show full text]
  • Histology of Muscle Tissue
    HISTOLOGY OF MUSCLE TISSUE Dr. Sangeeta Kotrannavar Assistant Professor Dept. of Anatomy, USM-KLE IMP, Belagavi Objectives Distinguish the microscopic features of • Skeletal • Cardiac • Smooth muscles Muscle • Latin musculus =little mouse (mus) • Muscle cells are known as MYOCYTES. • Myocytes are elongated so referred as muscle fibers Fleshy • Definition • Muscle is a contractile tissue which brings about movements Tendons Muscle makes up 30-35% (in women) & 40-45% (in men) of body mass Type of muscles BASED ON BASED ON BASED ON LOCATION STRIATIONS CONTROL Skeletal / Somatic STRIATED / STRIPED VOLUNTARY Smooth / Visceral UN-STRIATED / IN-VOLUNTARY UNSTRIPED Cardiac STRIATED / STRIPED IN-VOLUNTARY SKELETAL MUSCLE Skeletal muscle organization Muscles are complex structures: arranged in fascicles Muscle bundles / fascicles • Epimysium surrounds entire muscle – Dense CT that merges with tendon – Epi = outer, Mys = muscle • Perimysium surrounds muscle fascicles – Peri = around – Within a muscle fascicle are many muscle fibers • Endomysium surrounds muscle fiber – Endo = within SKELETAL MUSCLE • Each bundles contains many muscle fiber Structure of a skeletal muscle fiber • Elongated, unbranched cylindrical fibers • Length- 1 mm – 5 cm, Width – 10 mm - 100μm • Fibers have striations of dark & light bands • Many flat nuclei beneath sarcolemma • Plasma membrane = sarcolemma • Smooth endoplsmic reticulum = sarcoplasmic reticulum (SR) • Cytoplasm = sarcoplasm • Mitochondria = sarcosomes • Each muscle fiber made of long cylindrical myofibrils Structure
    [Show full text]
  • Muscle Contraction
    Muscle Physiology Dr. Ebneshahidi © 2009 Ebneshahidi Skeletal Muscle Figure 9.2 (a) © 2009 Ebneshahidi Functions of the muscular system . 1. Locomotion – body movements are due to skeletal muscle contraction. 2. Vasoconstriction and vasodilatation - constriction and dilation of blood vessel walls are the results of smooth muscle contraction. 3. Peristalsis – wavelike motion along the digestive tract is produced by the smooth muscle. 4. Cardiac motion – heart chambers pump blood to the lungs and to the body because of cardiac muscle contraction. 5. Posture maintenance - contraction of skeletal muscles maintains body posture and muscle tone. 6. Heat generation – about 75% of ATP energy used in muscle contraction is released as heat. © 2009 Ebneshahidi Comparison of the three types of muscle . Striation: only present in skeletal and cardiac muscles. Absent in smooth muscle. Nucleus: smooth and cardiac muscles are uninculcated (one nucleus per cell) skeletal muscle is multinucleated (several nuclei per cell). Transverse tubule (T tubule): well developed in skeletal and cardiac muscles to transport calcium. Absent in smooth muscle. Intercalated disk: specialized intercellular junction that only occurs in cardiac muscle. Control: skeletal muscle is always under voluntary control‚ with some exceptions (the tongue and pili arrector muscles in the dermis). Smooth and cardiac muscles are under involuntary control. © 2009 Ebneshahidi Innervation: motor unit . a) a motor nerve and a myofibril from a neuromuscular junction where gap (called synapse) occurs between the two structures. At the end of motor nerve‚ neurotransmitter (i.e. acetylcholine) is stored in synaptic vesicles which will release the neurotransmitter using exocytosis upon the stimulation of a nerve impulse.
    [Show full text]
  • Muscle Tissue[PDF]
    Muscle Tissue BY Dr Navneet Kumar Professor Anatomy KGMU LKO Dr Navneet Kumar Professor Anatomy KGMU LKO Muscle Tissue A muscle tissue is made of contractile cells Dr Navneet Kumar Professor Anatomy KGMU LKO Muscle Tissue • Types- • 1.Muscle tissue -Skeletal muscle -Smooth muscle -Cardiac muscle 2.Single cell unite -myoepithelial cells -myofibroblast cells Dr Navneet Kumar Professor Anatomy KGMU LKO Muscle Tissue Plasma membrane -Sarcolema Cytoplasm -Sarcoplasm Endoplasmic reticulum-Sarcoplasmic reticulum Mitochondria- -Sarcosome Dr Navneet Kumar Professor Anatomy KGMU LKO Skeletal muscle…. • Epi mysium • Peri mysium • Endo mysium Dr Navneet Kumar Professor Anatomy KGMU LKO SKELETAL MUSCLE Dr Navneet Kumar Professor Anatomy KGMU LKO Skeletal muscle • features • Skeletal muscle composed of muscle fibres • Each muscle fibre is an elongated unbranched cell, voluntary • Nuclei present at periphery • Striations, Alternative dark and light bands Dr Navneet Kumar Professor Anatomy KGMU LKO Skeletal muscle….. E.M. Structure • Muscle fibre or Muscle cell A muscle fibre (muscle cell) contains bundle of myofibril Myofibril • myofibrils are made of myofilaments Myofilament -Thick myofilaments- myosin protein -Thin myofilaments- actin protein Cross striations are the result of overlapping of myosin protein& actin protein - Transvers tubule system - triad Dr Navneet Kumar Professor Anatomy KGMU LKO Arrangement of myofibril Dr Navneet Kumar Professor Anatomy KGMU LKO Dr Navneet Kumar Professor Anatomy KGMU LKO Arrangement of Myofilament -Dark band-’A’
    [Show full text]
  • Muscle Tissue and Organization 289
    MUSCULAR SYSTEM OUTLINE 10.1 Properties of Muscle Tissue 289 10.2 Characteristics of Skeletal Muscle Tissue 289 10 10.2a Functions of Skeletal Muscle Tissue 289 10.2b Gross Anatomy of Skeletal Muscle 290 10.2c Microscopic Anatomy of Skeletal Muscle 293 10.3 Contraction of Skeletal Muscle Fibers 298 Muscle 10.3a The Sliding Filament Theory 298 10.3b Neuromuscular Junctions 298 10.3c Physiology of Muscle Contraction 301 10.3d Muscle Contraction: A Summary 303 Tissue and 10.3e Motor Units 303 10.4 Types of Skeletal Muscle Fibers 305 10.4a Distribution of Slow, Intermediate, and Fast Fibers 307 10.5 Skeletal Muscle Fiber Organization 307 Organization 10.5a Circular Muscles 307 10.5b Parallel Muscles 307 10.5c Convergent Muscles 307 10.5d Pennate Muscles 307 10.6 Exercise and Skeletal Muscle 309 10.6a Muscle Atrophy 309 10.6b Muscle Hypertrophy 309 10.7 Levers and Joint Biomechanics 309 10.7a Classes of Levers 309 10.7b Actions of Skeletal Muscles 310 10.8 The Naming of Skeletal Muscles 311 10.9 Characteristics of Cardiac and Smooth Muscle 312 10.9a Cardiac Muscle 312 10.9b Smooth Muscle 313 10.10 Aging and the Muscular System 313 10.11 Development of the Muscular System 317 MODULE 6: MUSCULAR SYSTEM mck78097_ch10_288-321.indd 288 2/14/11 3:42 PM Chapter Ten Muscle Tissue and Organization 289 hen most of us hear the word “muscle,” we think of the W muscles that move the skeleton. These muscles are con- 10.2 Characteristics of Skeletal sidered organs because they are composed not only of muscle Muscle Tissue tissue, but also of epithelial, connective, and nervous tissue.
    [Show full text]
  • Levels of Muscle Structure
    Levels of Muscle Structure • Muscle • Muscle Bundle • Muscle Fiber (myofiber) • Myofibrils • Myofilaments 1 Muscle Muscle Bundle • Contains 10-20 myofibers • Encased by perimysium • Can see with the naked eye Myofiber (Muscle fiber) • Individual muscle cell • Multinucleated • Encased by endomysium • Cell wall: sarcolemma 2 Myofibrils • Embedded in sarcoplasm • Mitochondria located between myofibrils Myofibrils • Comprised of repeating units: sarcomeres – A band – I band –Z disk –H zone – Pseudo-H zone 3 Sarcomere Sarcomere Myofilaments • Contractile Proteins – Myosin – Actin • Regulatory Proteins – Tropomyosin – Troponin • Structural Proteins – Z – Line Proteins 4 Contractile Proteins • Myosin – 70 – 80% of the total protein – Thick filament – Burns the ATP for muscle contraction Myosin & Its Fragments Chymotrypsin – Myosin head moves S1 back and forth to perform a muscle ROD Alkali Reg ula to r y li g ht c h ain - light chain COO contraction LMM COO- Actin binding and A TPa se activity HMM Trypsin Contractile Proteins • Actin – 20% of the myofibrillar protein – Thin Filament – Globular protein (G- protein) – Arranged like a twisted pearl necklace (F-protein) – Myosin head attaches to the Actin Regulatory Proteins • Regulate contraction and the speed of contraction • Tropomyosin • Troponin 5 Regulatory Proteins • Tropomyosin – Thin protein that lays around the Actin proteins AA End View Top View Regulatory Proteins • Troponin • 3 Subunits – TnT • Binds tropomyosin – TnI • Inhibitory subunit – TnC • Ca2+ binding subunit 3 Dimensional 6
    [Show full text]
  • Skletal Muscle Tissue
    SKELETAL MUSCLE Site • All skeletal muscle attached to skeleton. • Tongue. • Larynx. • Pharynx. • Eye. Types: – Striated Voluntary (under control of will) except:- – upper third of esophagus. – pharynx. – cremasteric muscle. • Do not branch Except:- – tongue and face. Structure of SK. M.: • It is formed of cells (fibers) and connective tissue. A. Connective tissue: 1-Epimysium • It is a dense C.T. which surround the whole muscle. 2-Perimysium • It is a dense C.T. which divides the muscle into bundles (each bundle contain a group of muscle fibers). 3-Endomysium: • It is a loose C.T. which separates the muscle fibers. Function of C.T.: • 1-It contains blood vessels, nerves and lymphatic. • 2-Give attachment between muscle bundles. • 3-Help the attachment of muscle to tendon, ligament, perichondrium and periostium. B- Skeletal Muscle F.: L/M of Sk. M. Fiber: T/S: -Polyhedral in shape. -100 um in diameter. -The nucleus is only seen in some fibers. -The sarcoplasm may show dark areas (Cohnheim's areas) due to grouping of the myofibrils. L/S: • Single elongated mutinucleated cell (syncytium). • 1-40 mm. in length. • 10-100 um in diameter. • Have multiple flattened oval peripherally situated nuclei. • Have regular transverse striation. • The sarcoplasm is acidophilic and contains: • B- Glycogen granules. • Myoglobin pigment. E/M of Skeletal Muscle Fiber: • The sarcoplasm show tubular envaginations (T.T.). • Plenty of mitochondria. • Smooth endoplasmic reticulum (arcoplasmic reticulum). • Ribosomes. • B- Glycogen granules. • Myoglobin pigment. • Myofibrils (sarcostyles) (Actin &Myosin F.) Myofibrils (Sarcostyles) Definition: • These are contractile elements which are longitudinally arranged in the sarcoplasm of the skeletal muscle fiber.
    [Show full text]
  • Cell Death, Clearance and Immunity in the Skeletal Muscle
    Cell Death and Differentiation (2016) 23, 927–937 & 2016 Macmillan Publishers Limited All rights reserved 1350-9047/16 www.nature.com/cdd Review Cell death, clearance and immunity in the skeletal muscle C Sciorati1, E Rigamonti1, AA Manfredi1,2 and P Rovere-Querini*,1,2 The skeletal muscle is an immunologically unique tissue. Leukocytes, virtually absent in physiological conditions, are quickly recruited into the tissue upon injury and persist during regeneration. Apoptosis, necrosis and autophagy coexist in the injured/ regenerating muscles, including those of patients with neuromuscular disorders, such as inflammatory myopathies, dystrophies, metabolic and mitochondrial myopathies and drug-induced myopathies. Macrophages are able to alter their function in response to microenvironment conditions and as a consequence coordinate changes within the tissue from the early injury throughout regeneration and eventual healing, and regulate the activation and the function of stem cells. Early after injury, classically activated macrophages (‘M1’) dominate the picture. Alternatively activated M2 macrophages predominate during resolution phases and regulate the termination of the inflammatory responses. The dynamic M1/M2 transition is increasingly felt to be the key to the homeostasis of the muscle. Recognition and clearance of debris originating from damaged myofibers and from dying stem/ progenitor cells, stromal cells and leukocytes are fundamental actions of macrophages. Clearance of apoptotic cells and M1/M2 transition are causally connected and represent limiting steps for muscle healing. The accumulation of apoptotic cells, which reflects their defective clearance, has been demonstrated in various tissues to prompt autoimmunity against intracellular autoantigens. In the muscle, in the presence of type I interferon, apoptotic myoblasts indeed cause the production of autoantibodies, lymphocyte infiltration and continuous cycles of muscle injury and regeneration, mimicking human inflammatory myopathies.
    [Show full text]
  • Ischemia Reperfusion Injury Produces, and Ischemic Preconditioning Prevents, Rat Cardiac Fibroblast Differentiation: Role of KATP Channels
    Journal of Cardiovascular Development and Disease Article Ischemia Reperfusion Injury Produces, and Ischemic Preconditioning Prevents, Rat Cardiac Fibroblast Differentiation: Role of KATP Channels 1, 2, 2 2, Kartika R. Pertiwi y , Rachael M. Hillman y, Coralie A. Scott and Emily Lisa Chilton * 1 Department of Biology Education, Faculty of Mathematics and Natural Science, Yogyakarta State University, Yogyakarta 55281, Indonesia; [email protected] 2 Physiology and Pharmacology, College of Public, Medical and Veterinary Sciences, James Cook University, 4814 Townsville, Queensland, Australia; [email protected] (R.M.H.); [email protected] (C.A.S.) * Correspondence: [email protected]; Tel.: +61-(0)7-4781-5195 These authors have contributed equally to this work. y Received: 18 April 2019; Accepted: 31 May 2019; Published: 4 June 2019 Abstract: Ischemic preconditioning (IPC) and activation of ATP-sensitive potassium channels (KATP) protect cardiac myocytes from ischemia reperfusion (IR) injury. We investigated the influence of IR injury, IPC and KATP in isolated rat cardiac fibroblasts. Hearts were removed under isoflurane anesthesia. IR was simulated in vitro by application and removal of paraffin oil over pelleted cells. Ischemia (30, 60 and 120 min) followed by 60 min reperfusion resulted in significant differentiation of fibroblasts into myofibroblasts in culture (mean % fibroblasts SEM in IR vs. time control: 12 1% ± ± vs. 63 2%, 30 min ischemia; 15 3% vs. 71 4%, 60 min ischemia; 8 1% vs. 55 2%, 120 min ± ± ± ± ± ischemia). IPC (15 min ischemia, 30 min reperfusion) significantly attenuated IR-induced fibroblast differentiation (52 3%) compared to 60 min IR.
    [Show full text]