US EPA

1450317 

Journal Article 

Function and Regulation of Isoforms of Carbon Monoxide Dehydrogenase/Acetyl Coenzyme A Synthase in Methanosarcina acetivorans 

Matschiavelli, N; Oelgeschlaeger, E; Cocchiararo, B; Finke, J; Rother, M 

2012 

Yes 

Journal of Bacteriology
ISSN: 0021-9193
EISSN: 1098-5530 

194 

19 

5377-5387 

22865842 

10.1128/JB.00881-12 

WOS:000308749700024 

Conversion of acetate to methane (aceticlastic
methanogenesis) is an ecologically important process carried out exclusively by methanogenic
archaea. An important enzyme for this process as well as for methanogenic growth on carbon
monoxide is the five-subunit archaeal CO dehydrogenase/acetyl coenzyme A (CoA) synthase
multienzyme complex (CODH/ACS) catalyzing both CO oxidation/CO2 reduction and cleavage/synthesis
of acetyl-CoA. Methanosarcina acetivorans C2A contains two very similar copies of a six-gene
operon (cdh genes) encoding two isoforms of CODH/ACS (Cdh1 and Cdh2) and a single CdhA subunit,
CdhA3. To address the role of the CODH/ACS system in M. acetivorans, mutational as well as
promoter/reporter gene fusion analyses were conducted. Phenotypic characterization of cdh
disruption mutants (three single and double mutants, as well as the triple mutant) revealed a
strict requirement of either Cdh1 or Cdh2 for acetotrophic or carboxidotrophic growth, as well as
for autotrophy, which demonstrated that both isoforms are bona fide CODH/ACS. While expression of
the Cdh2-encoding genes was generally higher than that of genes encoding Cdh1, both appeared to
be regulated differentially in response to growth phase and to changing substrate conditions.
While dispensable for growth, CdhA3 clearly affected expression of cdh1, suggesting that it
functions in signal perception and transduction rather than in catabolism. The data obtained
argue for a functional hierarchy and regulatory cross talk of the CODH/ACS isoforms.