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.

Gaseous O2, NO, and CO in Signal Transduction: Structure and Function Relationships of Heme-Based Gas Sensors and Heme-Redox Sensors

“…Heme-based redox sensors with c -type (covalently attached: Figure E) heme have been reported. − Importantly, autophosphorylation, perhaps as part of a two-component signal transduction system, is regulated by heme redox changes in MA4561, a heme-based sensor with a c -type heme . Among other heme-based sensors with c -type heme, including GSU582/GSU935, ,− DcrA has been extensively studied with respect to structural and physicochemical properties of the isolated heme domain . Unfortunately, catalytic and functional regulation of DcrA by heme redox changes has not been examined.…”

Dynamics of the His79-Heme Alkaline Transition of Yeast Iso-1-cytochrome c Probed by Conformationally Gated Electron Transfer with Co(II)bis(terpyridine)

“…1–5 In metalloprotions, the interconversion between alternate conformers can be driven by changes in metal ligation. 6–12 One of the most thoroughly studied ligand-mediated conformational changes for a metalloprotein is the alkaline conformational transition of mitochondrial cytochrome c (Cyt c ). 13,14 The alkaline conformational transition occurs at moderately alkaline pH and involves replacement of the Met80 ligand in the 6 th coordination site of the heme with either Lys73 or Lys79 in the heme crevice loop (residues 70–85, shown in red in Figure 1).…”

“…There has been considerable recent interest in characterizing alternate conformers of proteins because they are believed to be important for function. − In metalloprotions, the interconversion between alternate conformers can be driven by changes in metal ligation. − One of the most thoroughly studied ligand-mediated conformational changes for a metalloprotein is the alkaline conformational transition of mitochondrial cytochrome c (Cyt c ). , The alkaline conformational transition occurs at moderately alkaline pH and involves replacement of the Met80 ligand in the sixth coordination site of the heme with either Lys73 or Lys79 in the heme crevice loop (residues 70–85, shown in red in Figure ). , The Lys73- and Lys79-heme alkaline conformers are often assumed to be structurally and functionally equivalent. We apply conformationally gated electron-transfer (gated ET) methods to a K79H variant of yeast iso-1-cytochrome c , iso-1-Cyt c , to show that the mechanisms of formation of alkaline conformers with ligands from position 73 versus 79 differ.…”

Engineered living conductive biofilms as functional materials

“…A change in oxidation state and coordination of the bound heme is believed to result in a conformational change that activates or deactivates the catalytic domain. [77,78] Although the sensor domains of these proteins have been fairly well characterized in vitro the redox inputs that actuate the signaling cascade are unknown.…”