CODehydrogenase and Acetyl‐CoASynthase Assembly

Abstract

Ni,Fe‐containing carbon monoxide dehydrogenases (CODHs) and acetyl‐CoA synthases (ACSs) are ubiquitous among anaerobic bacteria and archaea. CODHs catalyze the reversible reduction of CO 2 with two electrons and two protons to CO and water. ACSs catalyze the reversible condensation of CO, coenzyme A, and a methyl cation to acetyl‐CoA, and both enzymes can occur in a monofunctional or as a stable bifunctional complex. Compared to what is known about the maturation of other Ni‐containing enzymes, how CODH and ACS mature is just beginning to emerge. Despite differences in active‐site metal content (CODH: 1xNi, 4xFe; ACS: 2xNi, 4xFe), architecture (CODH: Ni integrated in a NiFe 3 S 4 cubanoidal subcluster; ACS: two Ni next to a [4Fe4S] cluster), active‐site accessibility, and protein fold, both Ni,Fe‐clusters are matured by homologous ATPases of the MinD/Mrp‐family called CooC (CODH maturation) and AcsF (ACS maturation). CooC sustains the ATP‐dependent Ni insertion into the active‐site cluster of CODHs in the presence of physiological nickel concentrations. CooC can bind nickel at a GCXC motif in the dimer interface and ADP/ATP binding changes the coordination of nickel. AcsF forms a tight complex with Ni‐free ACS, together creating a binding platform for two nickel ions. The Ni‐loaded ACS–AcsF complex remains inactive until MgATP is added to it, resulting in fully active ACS. Details of the mechanisms and structures known to date are discussed in the chapter.