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PROTEINS

FOLDEDPOLYPEPTIDES

?2007PaulBillietODWSPRIMARYSTRUCTUREThesequenceofaminoacidsMIL1sequence:>gi|7662506|ref|NP_056182.1|MIL1protein[Homosapiens]MEDCLAHLGEKVSQELKEPLHKALQMLLSQPVTYQAFRECTLETTVHASGWNKILVPLVLLRQMLLELTRLGQEPLSALLQFGVTYLEDYSAEYIIQQGGWGTVFSLESEEEEYPGITAEDSNDIYILPSDNSGQVSPPESPTVTTSWQSESLPVSLSASQSWHTESLPVSLGPESWQQIAMDPEEVKSLDSNGAGEKSENNSSNSDIVHVEKEEVPEGMEEAAVASVVLPARELQEALPEAPAPLLPHITATSLLGTREPDTEVITVEKSSPATSLFVELDEEEVKAATTEPTEVEEVVPALEPTETLLSEKEINAREESLVEELSPASEKKPVPPSEGKSRLSPAGEMKPMPLSEGKSILLFGGAAAVAILAVAIGVALALRKKlength:386aminoacids?Anne-MarieTernes

PRIMARYSTRUCTUREThenumbersofaminoacidsvary

(e.g.insulin51,lysozyme129,haemoglobin574,gammaglobulin1250)TheprimarystructuredeterminesthefoldingofthepolypeptidetogiveafunctionalproteinPolaraminoacids(acidic,basicandneutral)arehydrophilicandtendtobeplacedontheoutsideoftheprotein.Non-polar(hydrophobic)aminoacidstendtobeplacedontheinsideoftheprotein?2007PaulBillietODWSInfinitevarietyThenumberofpossiblesequencesisinfinite

Anaverageproteinhas300aminoacids,

Ateachpositiontherecouldbeoneof20differentaminoacids

=10390possiblecombinationsMostareuseless

Naturalselectionpicksoutthebest?2007PaulBillietODWSSECONDARYSTRUCTURE

ThefoldingoftheN-C-Cbackboneofthepolypeptidechainusingweakhydrogenbonds

?ScienceStudent?Text2007PaulBillietODWSSECONDARYSTRUCTUREThisproducesthealphahelixandbetapleatingThelengthofthehelixorpleatisdeterminedbycertainaminoacidsthatwillnotparticipateinthesestructures

(line)?DrGaryKaiser

?Text2007PaulBillietODWSTERTIARYSTRUCTURE

ThefoldingofthepolypeptideintodomainswhosechemicalpropertiesaredeterminedbytheaminoacidsinthechainMIL1protein?Anne-MarieTernes

?2007PaulBillietODWSTERTIARYSTRUCTUREThisfoldingissometimesheldtogetherbystrongcovalentbonds

(e.g.cysteine-cysteinedisulphidebridge)Bendingofthechaintakesplaceatcertainaminoacids

(line)HydrophobicaminoacidstendtoarrangethemselvesinsidethemoleculeHydrophilicaminoacidsarrangethemselvesontheoutside?2007PaulBillietODWS?MaxPlanckInstituteforMolecularGeneticsChainBofProteinKinaseCQUATERNARYSTRUCTURESomeproteinsaremadeofseveralpolypeptidesubunits

(e.g.haemoglobinhasfour)ProteinKinaseC?MaxPlanckInstituteforMolecularGenetics?Text2007PaulBillietODWSQUATERNARYSTRUCTUREThesesubunitsfittogethertoformthefunctionalproteinTherefore,thesequenceoftheaminoacidsintheprimarystructurewillinfluencetheprotein'sstructureattwo,threeormorelevels?2007PaulBillietODWSResult

ProteinstructuredependsupontheaminoacidsequenceThis,inturn,dependsuponthesequenceofbasesinthegene

?2007PaulBillietODWSPROTEINFUNCTIONS

ProteinstructuredeterminesproteinfunctionDenaturationorinhibitionwhichmaychangeproteinstructurewillchangeitsfunctionCoenzymesandcofactorsingeneralmayenhancetheprotein'sstructure?2007PaulBillietODWSFibrousproteinsInvolvedinstructure:tendonsligamentsbloodclots

(e.g.collagenandkeratin)Contractileproteinsinmovement:muscle,microtubules

(cytoskelton,mitoticspindle,cilia,flagella)?2007PaulBillietODWSGlobularproteins

mostproteinswhichmovearound(e.g.albumen,caseininmilk)Proteinswithbindingsites:

enzymes,haemoglobin,immunoglobulins,membranereceptorsites?2007PaulBillietODWSProteinsclassifiedbyfunction

CATALYTIC:enzymesSTORAGE:ovalbumen(ineggs),casein(inmilk),zein(inmaize)TRANSPORT:haemoglobinCOMMUNICATION:hormones(eginsulin)andneurotransmittersCONTRACTILE:actin,myo