DOCSLIB.ORG

Skletal Muscle Tissue

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read 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. Structure: • The myofibril shows alternating light and dark bands. • The light band is not refractile in polarized microscope (Isotropic or I- band). and it is pale in living fibers. • The dark bands is double refractile in polarized microscope ( Anisotropic or A- band) and it is dark in fresh state. • Each dark band is divided at its center by a light disc called H- zone. • Each light band is divided at its center by a dark line called Z-line. The Sarcomere: • It is the area between two Z-lines. • It is the functional contractile unit of a myofibril. • It includes a whole A (dark band) and ½ of I (light band) on either side. • It contain minute structure called myofilaments Molecular structure of actin and myosin: 1-Actin molecule: • It is formed of : • 1- globular proteins (G-actin) which coiled around each other into a helix. • 2-A long narrow protein molecule called tropomyosin which is bound to the actin molecules along the length of the helix. • 3-Another globular protein called troponin which is attached to tropomyosin at regular intervals. 2-Myosin molecule: • It is shaped like a golf club. It has: • 1- a rod-like shaft (light meromyosin). • 2- a globular head (heavy meromyosin). The sarcolemma and the Conducting System for Contractile Stimuli It is a typical cell membrane which plays an important role in conducting the wave of excitation to the myofibril. It sends narrow tubular invagination called transverse tubules (T.T.) to encircle the sarcomeres like collars at the A-I junction. Triad of tubular system • This triad is formed of: • one transverse tubule (T.T) • two terminal cisternae or sarcoplasmic reticulum (S.R.). 1) T.T: • These are transverse tubules which are invaginated from the sarcolemma. • They form a collar around the myofibrils at the junction between the A and I bands (A-I junction). 2) S.R. : • The sarcoplasmic reticulum is formed of small tubules. • It forms a fenestrated collar around sarcomere. • It terminates by two wide tubules called terminal cisternae (one on each side of the T.T.) at the A-I junction. N.B.:Each sarcromere has two triads. Role of this triad in contraction: • When a nerve impulses are transmitted to the Sarcoplasm, It is transmitted to the sarcoplasmic reticulum via the T.T of the triads. • The SR will pump Ca ions into the myofibrils. • The energy rich-ATP of the muscle is converted into ADP with the release of energy. • This energy allows the actin to interact with myosin and cause gliding of thin filaments over thick filaments and ensure a proper union between them. • The thin filaments slide towards the middle of the sarcomere, pulling the 2 ''Z''- lines behind them. • This allow shortening of sarcomere and lead to muscle contraction and loss of H- zone. Development of the muscle fibers: In Embryo • The muscle fibers is formed by fusion of mono nucleated cells (Myoblasts). In Adults • It develops several nuclei by fusion of myofibroblast present close to the) )cell membrane called satellite .cells Repair of the Muscle Fiber: • By the activity of satellite cells. • Differentiating into muscle fibers. Changes at the musculo-tendinous junction • Connective tissue Continuous into and blend with C.T. of the tendon. • Muscle fibers stop suddenly. • The sarcolemma blends firmly with the C.T. of the tendon. • The myofibrils stop at this junction. .
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]
  • Massive Alterations of Sarcoplasmic Reticulum Free Calcium in Skeletal Muscle Fibers Lacking Calsequestrin Revealed by a Genetic
    Massive alterations of sarcoplasmic reticulum free calcium in skeletal muscle fibers lacking calsequestrin revealed by a genetically encoded probe M. Canatoa,1, M. Scorzetoa,1, M. Giacomellob, F. Protasic,d, C. Reggiania,d, and G. J. M. Stienene,2 Departments of aHuman Anatomy and Physiology and bExperimental Veterinary Sciences, University of Padua, 35121 Padua, Italy; cCeSI, Department of Basic and Applied Medical Sciences, University G. d’Annunzio, I-66013 Chieti, Italy; dIIM-Interuniversity Institute of Myology and eLaboratory for Physiology, Institute for Cardiovascular Research, VU University Medical Center, 1081BT, Amsterdam, The Netherlands Edited* by Clara Franzini-Armstrong, University of Pennsylvania Medical Center, Philadelphia, PA, and approved November 12, 2010 (received for review June 30, 2010) The cytosolic free Ca2+ transients elicited by muscle fiber excitation tion essential to maintain a low metabolic rate in quiescent ex- are well characterized, but little is known about the free [Ca2+] citable cells. In addition, CSQ has been shown to modulate RyR- dynamics within the sarcoplasmic reticulum (SR). A targetable mediated Ca2+ release from the SR (6). To understand the pivotal ratiometric FRET-based calcium indicator (D1ER Cameleon) allowed role of CSQ in SR function, it is critical to determine free SR us to investigate SR Ca2+ dynamics and analyze the impact of cal- Ca2+ concentration, and this has been made possible by the ad- sequestrin (CSQ) on SR [Ca2+] in enzymatically dissociated flexor vent of a targetable ratiometric FRET-based indicator, such as digitorum brevis muscle fibers from WT and CSQ-KO mice lacking D1ER Cameleon (7). Seminal studies using this technique have isoform 1 (CSQ-KO) or both isoforms [CSQ-double KO (DKO)].
    [Show full text]
  • Localization of Ca2l Release Channels with Ryanodine in Junctional
    Proc. NatI. Acad. Sci. USA Vol. 82, pp. 7256-7259, November 1985 Biochemistry Localization of Ca2l release channels with ryanodine in junctional terminal cisternae of sarcoplasmic reticulum of fast skeletal muscle (muscle contraction/excitation-contraction coupling/ruthenium red/longitudinal cisternae/gated channels) SIDNEY FLEISCHER, EUNICE M. OGUNBUNMI, MARK C. DIXON, AND EDUARD A. M. FLEER Department of Molecular Biology, Vanderbilt University, Nashville, TN 37235 Communicated by William J. Darby, July 8, 198S ABSTRACT The mechanism of Ca2' release from tional terminal cisternae consist of two types of membranes, sarcoplasmic reticulum, which triggers contraction in skeletal the Ca2l pump membrane (80-85%) and the junctional face muscle, remains the key unresolved problem in excita- membrane (15-20%) (16). A unique characteristic of junc- tion-contraction coupling. Recently, we have described the tional terminal cisternae is that they have a poor Ca2+ loading isolation of purified fractions referable to terminal and longi- rate, which can be enhanced 5-fold or more by addition of tudinal cisternae of sarcoplasmic reticulum. Junctional termi- ruthenium red (RR) (ref. 17; unpublished data). This study nal cisternae are distinct in that they have a low net energized describes the drug action of ryanodine on the junctional Ca2+ loading, which can be enhanced 5-fold or more by terminal cisternae in blocking the action of RR. It provides addition of ruthenium red. The loading rate, normalized for evidence that the action of ryanodine is on the Ca2' release calcium pump protein content, then approaches that of longi- mechanism and supports the view that Ca2' release is tudinal cisternae of sarcoplasmic reticulum.
    [Show full text]
  • Ultra-High Resolution Scanning Electron Microscopic Studies on the Sarcoplasmic Reticulum and Mitochondria in Various Muscles: a Review
    Scanning Microscopy Volume 7 Number 1 Article 16 12-29-1992 Ultra-High Resolution Scanning Electron Microscopic Studies on the Sarcoplasmic Reticulum and Mitochondria in Various Muscles: A Review Takuro Ogata Kochi Medical School Yuichi Yamasaki Kochi Medical School Follow this and additional works at: https://digitalcommons.usu.edu/microscopy Part of the Biology Commons Recommended Citation Ogata, Takuro and Yamasaki, Yuichi (1992) "Ultra-High Resolution Scanning Electron Microscopic Studies on the Sarcoplasmic Reticulum and Mitochondria in Various Muscles: A Review," Scanning Microscopy: Vol. 7 : No. 1 , Article 16. Available at: https://digitalcommons.usu.edu/microscopy/vol7/iss1/16 This Article is brought to you for free and open access by the Western Dairy Center at DigitalCommons@USU. It has been accepted for inclusion in Scanning Microscopy by an authorized administrator of DigitalCommons@USU. For more information, please contact [email protected]. Scanning Microscopy, Vol. 7, No. 1, 1993 (Pages 145-156) 0891-7035/93$5 .00+ .00 Scanning Microscopy International, Chicago (AMF O'Hare), IL 60666 USA ULTRA-HIGH RESOLUTION SCANNING ELECTRON MICROSCOPIC STUDIES ON THE SARCOPLASMIC RETICULUM AND MITOCHONDRIA IN VARIOUS MUSCLES: A REVIEW Takuro Ogata* and Yuichi Yamasaki Department of Surgery, Kochi Medical School Nankoku, Kochi, 783 Japan (Received for publication March 23, 1992, and in revised form December 29, 1992) Abstract Introduction The three-dimensional structure of the sarco­ The three-dimensional models of the membrane plasm.ic
    [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]
  • Frog Skeletal Muscle Contraction Experiment
    Frog Skeletal Muscle Contraction Experiment Is Ajai Hitlerite or cheliferous when swage some cubist daut capriciously? Martyn remains Neozoic: she herald her waterfront militates too iniquitously? Lyle remains piscatorial after Tibold disavows loud or mazes any clubbing. Curare is also known among indigenous peoples as Ampi, Woorari, Woorara, Woorali, Wourali, Wouralia, Ourare, Ourari, Urare, Urari, and Uirary. The secondå°• major difference between plant and animal cells is the cell wall. In B, note the half pillar protruding from the TC, also indicated by a line. You seem to have javascript disabled. Neurophysiology of the neuromuscular junction: overview. The influence of activity on some contractile characteristics of mammalian fast and slow muscles. What was the smallest current required to produce each of the following? Kullberg R, Owens JL. It often resolves without treatment. This electrical signal is communicated to the myofilaments inside the fibre in the following way. Connective tissue cells, fibers and intercellular medium are present in these tissues; The cells of these tissues are widely spaced and forms intercellular matrix. When the current reached the following stages, what proportion of fibers in the muscle were contracting? Most land animals, including humans, depend on angiosperms directly or indirectly for sustenance. These cells are actively mitotic, producing new cells that get pushed upward into the overlying layers. Shaded bars represent periods of strain heterogeneity. Now, gradually flex your wrist back to a straight or neutral position. Summation of twitch responses Recoding a double contraction. Since it was too expensive to be used in warfare, curare was mainly used during hunting. Tension responses to sudden length change in stimulated frog muscle fibres near slack length.
    [Show 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.
    [Show full text]