Competition between reversible aggregation and loop formation in denatured iso-1-cytochrome c.

ABSTRACT: The competition between intramolecular histidine-heme loop formation and ligand-mediated oligomer formation in the denatured state is investigated for two yeast iso-1-cytochrome c variants, AcH26I52 and AcA25H26I52. Besides the native His 18 heme ligand, both variants contain a single His at position 26. The AcA25H26I52 variant has Pro 25 mutated to Ala. The concentration dependence of the apparent pK(a) for His 26-heme binding in 3 M guanidine hydrochloride indicates that the P25A mutation disfavors oligomerization mediated by intermolecular heme ligation by 10-fold. Single- and double-pH-jump stopped-flow experiments with the AcH26I52 variant show that fast phases for His-heme bond formation and breakage are due to intramolecular loop formation and slow phases for His-heme bond formation

SUBMITTER: Tzul FO 

PROVIDER: S-EPMC2645900 | biostudies-literature | 2009 Jan

REPOSITORIES: biostudies-literature