title: Cytochrome c(553), a small heme protein that lacks misligation in its unfolded state, folds with rapid two-state kinetics.
abstract: Cytochrome c(553) (cyt c(553)) from Desulfovibrio vulgaris is a small helical heme protein that displays apparent two-state equilibrium-unfolding behavior. The covalently attached heme is low-spin, ligated by Met and His residues, in the native state but becomes high-spin upon unfolding at pH 7. Here, we show that in contrast to other c-type heme proteins, where misligations in the unfolded states are prominent, cyt c(553) refolding kinetics at pH 7 proceeds rapidly without detectable intermediates. The extrapolated folding rate constant in water for oxidized cyt c(553) matches exactly that predicted from the cyt c(553) native-state topology: 5300 s(-1 )(experimental) versus 5020 s(-1) (predicted). We therefore conclude that the presence of the oxidized cofactor does not affect the intrinsic formation speed of the cyt c(553 )structural motif.
authors.affiliation: Chemistry Department, Tulane University, 6823 St. Charles Avenue, New Orleans, LA 70118, USA.
authors.forename: J
authors.initials: J
authors.lastname: Guidry
authors.forename: P
authors.initials: P
authors.lastname: Wittung-Stafshede
mesh_terms: D003574:Cytochrome c Group / Q000737:chemistry* / Q000378:metabolism*; D016969:Desulfovibrio vulgaris / Q000737:chemistry*; D019791:Guanidine / Q000494:pharmacology; D006639:Histidine / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008715:Methionine / Q000378:metabolism; D008958:Models, Molecular; D010084:Oxidation-Reduction; D011489:Protein Denaturation / Q000187:drug effects; D017510:Protein Folding; D020673:Protein Renaturation / Q000187:drug effects; D013816:Thermodynamics; D014867:Water / Q000378:metabolism
chemical_list: D003574:Cytochrome c Group; C083951:cytochrome c553; D014867:Water; D006639:Histidine; D008715:Methionine; D019791:Guanidine