title: Equilibrium folding intermediates of a Greek key beta-barrel protein.
abstract: Protein S is a calcium-binding protein comprising two Greek key beta-barrel domains. We have used NMR and optical spectroscopies to show that, in the absence of calcium, the N-terminal domain of protein S forms two equilibrium folding intermediates that are in slow exchange. The intermediates arise from differential calcium-dependent folding of subdomains which are not contiguous along the polypeptide chain. The structures of these intermediates are incompatible with several previously proposed folding mechanisms for Greek key beta-barrel domains. We proposed a different mechanism that involves multiple nucleation sites for folding and sequential acquisition of native long-range interactions.
authors.affiliation: Division of Molecular and Structural Biology, Ontario Cancer Institute, University of Toronto, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Bagby
authors.forename: S
authors.initials: S
authors.lastname: Go
authors.forename: S
authors.initials: S
authors.lastname: Inouye
authors.forename: M
authors.initials: M
authors.lastname: Ikura
authors.forename: A
authors.initials: A
authors.lastname: Chakrabartty
mesh_terms: D002118:Calcium / Q000378:metabolism; D002942:Circular Dichroism; D003198:Computer Simulation; D007700:Kinetics; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D011489:Protein Denaturation; D017510:Protein Folding; D017293:Protein S / Q000737:chemistry* / Q000378:metabolism; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013050:Spectrometry, Fluorescence / Q000379:methods; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D014508:Urea
chemical_list: D017293:Protein S; D011994:Recombinant Proteins; D014508:Urea; D002118:Calcium