Structure of the α ₂ ε ₂ Ni-dependent CO dehydrogenase component of the Methanosarcina barkeri acetyl-CoA decarbonylase/synthase complex

Abstract

Ni-dependent carbon monoxide dehydrogenases (Ni-CODHs) are a diverse family of enzymes that catalyze reversible CO:CO2 oxidoreductase activity in acetogens, methanogens, and some COusing bacteria. Crystallography of Ni-CODHs from CO-using bacteria and acetogens has revealed the overall fold of the Ni-CODH core and has suggested structures for the C cluster that mediates CO:CO2 interconversion. Despite these advances, the mechanism of CO oxidation has remained elusive. Herein, we report the structure of a distinct class of Ni-CODH from methanogenic archaea: the ␣2 2 component from the ␣8␤8␥8␦8 8 CODH/acetyl-CoA decarbonylase/ synthase complex, an enzyme responsible for the majority of biogenic methane production on Earth. The structure of this Ni-CODH component provides support for a hitherto unobserved state in which both CO and H2O/OH -bind to the Ni and the exogenous FCII iron of the C cluster, respectively, and offers insight into the structures and functional roles of the -subunit and FeS domain not present in nonmethanogenic Ni-CODHs.carbon dioxide ͉ carbon monoxide ͉ oxidoreductase ͉ acetate ͉ methanogenesis

CO in methanogenesis

“…The CdhAE component has CO dehydrogenase activity with ferredoxin as the electron acceptor (Terlesky and Ferry 1988a, b;Fischer and Thauer 1990). The crystal structure (Gong et al 2008) of the M. barkeri CdhAE (Fig. 6) shows a α 2 ε 2 configuration with the α subunit harboring a Ni-Fe-S C cluster and four Fe 4 S 4 clusters (B, D, E, and F in Fig.…”

Tight Coupling of Partial Reactions in the Acetyl-CoA Decarbonylase/Synthase (ACDS) Multienzyme Complex from Methanosarcina thermophila

“…The acetylenzyme intermediate is postulated to be a Ni p 2ϩ -acetyl species, in which the two low potential redox equivalents required for its formation are effectively trapped (16). Other characterized partial reactions of ACDS subcomponents include the rapid, reversible transfer of a methyl group between the ␥␦ corrinoid cofactor and substrate H 4 SPt, and the oxidation of CO derived from the carbonyl group of acetyl-CoA, catalyzed by the ␣ 2 ⑀ 2 subcomponent, for which an x-ray crystallographic structure is available for the protein from Methanosarcina barkeri (17).…”

The extended reductive acetyl-CoA pathway: ATPases in metal cluster maturation and reductive activation

“…All CODHs contain additional [4Fe-4S] clusters with short intercluster distances allowing rapid electron transfer ( Figure 2A) Drennan et al, 2001Drennan et al, , 2004Doukov et al, 2002;Darnault et al, 2003;Jeoung and Dobbek, 2007b;Gong et al, 2008). One [4Fe-4S] cluster termed cluster D is found in the dimer interface and is coordinated by two cysteine residues from each monomer.…”