Tight binding of heme to Staphylococcus aureus IsdG and IsdI precludes design of a competitive inhibitor.

ABSTRACT: The micromolar equilibrium constants for heme dissociation from IsdG and IsdI reported in the literature call into question whether these enzymes are actually members of the iron-regulated surface determinant system of Staphylococcus aureus, which harvests heme iron from a host during infection. In order to address this question, the heme dissociation constants for IsdG and IsdI were reevaluated using three approaches. The heme dissociation equilibrium constants were measured using a UV/Vis absorption-detected assay analyzed with an assumption-free model, and using a newly developed fluorescence-detected assay. The heme dissociation rate constants were estimated using apomyoglobin competition assays. Analyses of the UV/Vis absorption data revealed a critical flaw in the previous measuremen

SUBMITTER: Conger MA 

PROVIDER: S-EPMC5510889 | biostudies-literature | 2017 May

REPOSITORIES: biostudies-literature