Folding intermediates in cytochrome c.
Folding of cytochrome c from its low pH guanidine hydrochloride (Gdn-HCl) denatured state revealed a new intermediate, a five-coordinate high spin species with a water molecule coordinated to the heme. Incorporation of this five-coordinated intermediate into the previously reported ligand exchange model can quantitatively account for the observed folding kinetics. In this new model, unfolded cytochrome c is converted to its native structure through an obligatory folding intermediate, the histidine-water coordination state, whereas the five-coordinate state and a bis-histidine state are off-pathway intermediates. When the concentration of Gdn-HCl in the refolding solution was increased, an acceleration of the conversion from the bis-histidine coordinated state to the histidine-water coordinated state was observed, demonstrating that the reaction requires unfolding of the mis-organized polypeptide structure associated with the bis-histidine state.
Yeh
S R
SR
Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, New York 10461, USA. SYEH@AECOM.YU.EDU
Rousseau
D L
DL
D000595:Amino Acid Sequence; D000818:Animals; D003574:Cytochrome c Group / Q000737:chemistry* / Q000378:metabolism*; D019791:Guanidine; D006736:Horses; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008929:Mitochondria, Heart / Q000378:metabolism; D008958:Models, Molecular; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D013059:Spectrum Analysis, Raman / Q000379:methods; D013816:Thermodynamics
D003574:Cytochrome c Group; D019791:Guanidine