生物信息学：导论与方法 Bioinformatics: Introduction and Methods

https://www.coursera.org/course/pkubioinfo 生物信息学：导论与方法 Bioinformatics: Introduction and Methods

北京大学生物信息学中心高歌、魏丽萍 Ge Gao & Liping Wei Center for Bioinformatics, Peking University Sequence Database Search

北京大学生物信息学中心高歌 Ge Gao, Ph.D. Center for Bioinformatics, Peking University Unit 1: Sequence Databases 北京大学生物信息学中心高歌 Ge Gao, Ph.D. Center for Bioinformatics, Peking University S S - T - T ( Russ Altman BMI214)

Global alignment (Needleman‐Wunsch) Local alignment (Smith‐Waterman)

F 0,0  0 F 0 ,0   0   F i 1, j  1  s x i , y j  F i  1, j  1  s x i , y j   F i, j  max  F i  1, j  d F i , j  max  F i  1, j  d   F i , j  1  d  F i, j  1  d   0

“How can we determine the similarity between two sequences?”

Why is it important? • Similar sequence  Similar structure  Similar function (The “Sequence‐ to‐Structure‐to‐Function Paradigm”) • Similar sequence  Common ancestor (“Homology”)

• Or, identify similarities between – novel query sequence whose structures and functions are usually unknown and/or uncharacterized – sequences in (public) databases whose structures and functions have been elucidated and annotated.

• Statistically significant hits are assumed to be related to the query sequence – Similar function/structure – Common evolutionary ancestor

Get the inputted query

Get a database sequence

Run pair‐wise global/local alignment between query and database sequence

xi aligned to yj F i  1, j  1  sxi , y j   F i, j  max F i  1, j  d xi aligned to a gap   y aligned to a gap F i, j  1  d j

X F i  1, j  1 F i, j  1 Y d sxi , y j 

F i  1, j  d F i, j 

• Most recent release of human‐curated Swiss‐Prot protein databases contains 540,958 sequences with 192,206,270 amino acids (Sept 18th, 2013); – On average, the sequence length is 192,206,270/540,958 = 355.30 aa

• And assume your super‐fast computer can run one operation in 1μs = (0.000001s)

• Then, you will need 7.8 hr for ONE comparison!

Source: http://www.ebi.ac.uk/uniprot/TrEMBLstats

× 3 log2(bp) = ‐1.2 10 + 0.59y log (bp) = ‐4.6×103 + 2.3y 2 ‐16 2 R = 0.97, p‐value < 2.2×10 R2 = 0.97, p‐value < 2.2×10‐16 Doubling every 20 months Doubling every 5 months!

xi aligned to yj F i  1, j  1  sxi , y j   F i, j  max F i  1, j  d xi aligned to a gap   y aligned to a gap F i, j  1  d j

X F i  1, j  1 F i, j  1 Y d sxi , y j 

F i  1, j  d F i, j 

F i  1, j  d F i, j x y

• To make the alignment effectively, a Heuristic algorithm BLAST (Basic Local Alignment Search Tool) is proposed by Altschul et al in 1990.

• BLAST finds the highest scoring locally optimal alignments between a query sequence and a database. – Very fast algorithm – Can be used to search extremely large databases – Sufficiently sensitive and selective for most purposes – Robust –the default parameters just work for most cases

Copyright © Peking University Copyright © Peking University Copyright © Peking University Copyright © Peking University Copyright © Peking University data knowledge protein sequence functional information

(Modified from http://education.expasy.org/cours/Turin/UniProtKB_Turin.ppt) Copyright © Peking University (Modified from http://education.expasy.org/cours/Turin/UniProtKB_Turin.ppt) Copyright © Peking University (Modified from http://education.expasy.org/cours/Turin/UniProtKB_Turin.ppt)

Manual annotation Function, Subcellular location, Protein and gene names Catalytic activity, Disease, Taxonomic information Tissue specificty, Pathway…

MSKEKFERTKPHVNVGTIGHVDHGKTTLTAAITTVLAKTYGGAAR AFDQIDNAPEEKARGITINTSHVEYDTPTRHYAHVDCPGHADYVK NMITGAAQMDGAILVVAATDGPMPQTREHILLGRQVGVPYIIVFL References One protein sequence Manual annotation NKCDMVDDEELLELVEMEVRELLSQYDFPGDDTPIVRGSALKALE Post-translational modifications, GDAEWEAKILELAGFLDSYIPEPERAIDKPFLLPIEDVFSISGRGOne gene TVVTGRVERGIIKVGEEVEIVGIKETQKSTCTGVEMFRKLLDEGROne species variants, transmembrane domains, AGENVGVLLRGIKREEIERGQVLAKPGTIKPHTKFESEVYILSKD signal peptide… EGGRHTPFFKGYRPQFYFRTTDVTGTIELPEGVEMVMPGDNIKMV VTLIHPIAMDDGLRFAIREGGRTVGAGVVAKVLG

Alternative products: protein sequences produced by alternative splicing, Manual annotation Cross-references alternative promoter usage, Keywords to over 125 databases alternative initiation… and Gene Ontology

UniProtKB/Swiss-Prot www.uniprot.org Copyright © Peking University Organism-specific Genome annotation Polymorphism Family and domain AGD Sequence Proteomic Gene3D ArachnoServer Ensembl dbSNP EMBL PeptideAtlas HAMAP CGD IPI PRIDE EnsemblBacteria ConoServer InterPro EnsemblFungi PANTHER CTD PIR ProMEX Pfam CYGD RefSeq EnsemblMetazoa dictyBase EnsemblPlants PIRSF UniGene PRINTS EchoBASE Gene expression EnsemblProtists ProDom EcoGene euHCVdb ArrayExpress GeneID PROSITE SMART EuPathDB GenomeReviews Bgee SUPFAM FlyBase CleanEx KEGG TIGRFAMs GeneCards NMPDR GeneDB_Spombe Genevestigator Protein family/group GeneFarm GermOnline TIGR GenoList UCSC Allergome Gramene Ontologies VectorBase CAZy H-InvDB MEROPS HGNC GO PeroxiBase HPA PptaseDB LegioList REBASE Leproma UniProtKB/Swiss-Prot: TCDB MaizeGDB MGI 2D gel MIM 129 explicit links 2DBase-Ecoli neXtProt ANU-2DPAGE Orphanet Aarhus/Ghent-2DPAGE (no server) PharmGKB COMPLUYEAST-2DPAGE PseudoCAP and 14 implicit links! Cornea-2DPAGE RGD DOSAC-COBS-2DPAGE SGD ECO2DBASE (no server) OGP TAIR PHCI-2DPAGE TubercuList PMMA-2DPAGE WormBase Rat-heart-2DPAGE Xenbase REPRODUCTION-2DPAGE ZFIN Siena-2DPAGE 3D structure SWISS-2DPAGE Phylogenomic dbs UCD-2DPAGE eggNOG Other PPI DisProt World-2DPAGE PTM HSSP GeneTree BindingDB DIP Enzyme and pathway HOGENOM GlycoSuiteDB PDB DrugBank IntAct BioCyc HOVERGEN PhosphoSite PDBsum InParanoid NextBio MINT BRENDA ProteinModelPortal OMA PhosSite PMAP-CutDB STRING Pathway_Interaction_DB OrthoDB SMR Reactome PhylomeDB ProtClustDB (Modified from http://education.expasy.org/cours/Turin/UniProtKB_Turin.ppt) Copyright © Peking University Copyright © Peking University Summary

Domain(s)

Hits summary

HBB_HUMAN

Smith‐Waterman Local alignment

BLAST Local alignment

Copyright © Peking University Copyright © Peking University Copyright © Peking University Copyright © Peking University Copyright © Peking University Copyright © Peking University Summary Questions • Why do we need to perform a database searching?

• What’s the major challenge/obstacle when searching sequence database?

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