lecture 5 - 5-1MCB354Lecture 5Reading in Lehninger:Chapter...

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Unformatted text preview: 5-1MCB354Lecture 5Reading in Lehninger:Chapter 4Tertiary and Quaternary Structure of ProteinsMotifsDomains5-23-D foldingof a polypeptide:i) simple combinations of 2° structuralelements = “motifs”ii) combination of motifs into “domains”Tertiary structure3D Structure of globular proteins•Conformation: spatial arrangement of atoms in a protein•Polypeptide chains folded into spherical or globular shapes•Often contain several types of 2° structure•Many different 3D structures, many different functionseg. enzymes and regulatory proteins•Conformational changes possible(usually depend on binding of a ligand)•Hierarchical classification of protein structure:motifsand domains5-35-4•Motifs = stable arrangements of a few elements of 2° structurehelix-loop-helixorhelix-turn-helixEF-hand motif in Ca2+-binding proteinseg. in DNA-binding proteinsCommon structural motifs in globular proteinsDNA-binding Helix-Loop-Helix5-5β-α-βmotifhairpin-βmotifantiparallel strandsActive site αα(= those involvedin catalysis)often in this loopparallel strands5-6Common structural motifs in globular proteinsA Peptide Inhibitor (stable β-hairpin)5-7“Greek key motif”5-8Common structural motifs in globular proteins4 adjacent antiparallel βstrandsMany arrangements of β-strands are possible# of strands, their relative orientation, and how the strands are connectedalong the polypeptide chain (= strand order) vary, e.g.:No knots!Color coding is justintended to help identifyeach β-stand in 3D structure5-9Extended β-sheets can roll up to form β-barrels:5-10Pore-formingToxin from S. aureus5-11•Several motifsform a protein domain•= fundamental unit of tertiary structure•one polypeptide chain can have several domainsDomains5-12Domains May Have Distinct Functions, Even When Separated from Other DomainsTroponin C:each domaincan individuallybind Calcium5-13The Two Domains of Troponin C5-14Calmodulin: a classic EF-hand motif 5-15...
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lecture 5 - 5-1MCB354Lecture 5Reading in Lehninger:Chapter...

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