title: Changes in the heme ligation during folding of a Geobacter sulfurreducens sensor GSU0935.
abstract: Ligand binding and substitution reactions are important for metalloprotein folding and function. The heme sensor of a methyl-accepting chemotaxis GSU0935 is a c-type cytochrome from the bacterium Geobacter sulfurreducens. The heme domain switches one of its axial ligands from H(2)O to a low-spin ligand, presumably Met, upon reduction. The study analyzes the stability and folding kinetics of the ferric domain. Guanidine hydrochloride denaturation yields the low-spin heme species arising from coordination of the ferric heme by non-native His residues. The population of the low-spin species further increases and then declines during protein refolding. Kinetics and mutational effects suggest that His54, from the N-terminal region of the domain, is the transient ligand to the heme. The capture and release of a non-native ligand within the compact partially-folded structures illustrates the flexibility of the heme environment in GSU0935, which may relate to the domain sensor function.
authors.affiliation: Department of Chemistry, Dartmouth College, Hanover, NH 03755, USA.
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Freeman
authors.forename: Yuning
authors.initials: Y
authors.lastname: Hong
authors.forename: Katherine H
authors.initials: KH
authors.lastname: Schiavoni
authors.forename: D M Indika
authors.initials: DM
authors.lastname: Bandara
authors.forename: Ekaterina V
authors.initials: EV
authors.lastname: Pletneva
mesh_terms: D019943:Amino Acid Substitution; D003574:Cytochrome c Group / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D045302:Geobacter / Q000378:metabolism*; D019791:Guanidine / Q000737:chemistry; D006418:Heme / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008024:Ligands; D010084:Oxidation-Reduction; D058849:Protein Refolding; D017434:Protein Structure, Tertiary; D014867:Water / Q000737:chemistry
chemical_list: D003574:Cytochrome c Group; D008024:Ligands; D014867:Water; D006418:Heme; D019791:Guanidine