title: The off-pathway status of the alkali molten globule is unrelated to heme misligation and trans-pH effects: experiments with ferrocytochrome c.
abstract: The relevance of the alkali molten globule (B-state) to the folding pathway of cytochrome c has been studied further with the reduced state of the protein for which the B-state is prepared by ligating the ferrous heme iron with extrinsic CO under 1 mM gas concentration in the presence of NaCl. The CO derivative of ferrocytochrome c is desirable not only because it abrogates the interference of non-native heme ligands but the GdnHCl-unfolded protein refolds fast without deviating from the intrinsic folding pathway of the protein. Interstate folding-unfolding kinetics at alkaline and neutral pH conditions reveal that the B-state chain initially expands in the submillisecond regime in order to fold correctly to the native state. In this sense, it is an off-pathway nonproductive species which must dissipate some non-native elements before proceeding to fold. It is concluded that the alkali molten globule does not correspond to any possible transient structure in the folding pathway of cytochrome c.
authors.affiliation: School of Chemistry, University of Hyderabad, Hyderabad 500046, India. akbsc@uohyd.ernet.in
authors.forename: Abani K
authors.initials: AK
authors.lastname: Bhuyan
mesh_terms: D000468:Alkalies / Q000378:metabolism; D045304:Cytochromes c / Q000737:chemistry* / Q000378:metabolism; D006418:Heme / Q000737:chemistry / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008024:Ligands; D017510:Protein Folding
chemical_list: D000468:Alkalies; D008024:Ligands; D006418:Heme; D045304:Cytochromes c