The off-pathway status of the alkali molten globule is unrelated to heme misligation and trans-pH effects: experiments with ferrocytochrome c.
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.
Bhuyan
Abani K
AK
School of Chemistry, University of Hyderabad, Hyderabad 500046, India. akbsc@uohyd.ernet.in
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
D000468:Alkalies; D008024:Ligands; D006418:Heme; D045304:Cytochromes c