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

Abstract

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/CO 2 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.

Short-Term Exposure of Paddy Soil Microbial Communities to Salt Stress Triggers Different Transcriptional Responses of Key Taxonomic Groups

“…This complex cleaves acetyl-CoA into a methyl group, an enzyme-bound carbonyl, and free CoA. The methyl group is transferred by CODH/ACS to the C 1 -transferring cofactor tetrahydrosarcinapterin and subsequently reduced to methane (Matschiavelli et al, 2012). Concomitantly, methanosarcinal transcripts encoding methanogenesis were significantly enriched under salt stress.…”

Energy Conservation Associated with Ethanol Formation from H 2 and CO 2 in Clostridium autoethanogenum Involving Electron Bifurcation

“…In this respect, it is of interest that the genome of Methanosarcina acetivorans harbors one gene for CO dehydrogenase in a cluster with a gene for acetyl-CoA synthase and an orphan gene for CO dehydrogenases, either one of which can be disrupted without affecting growth of the methanogen on CO, methanol, or acetate, indicating that each of the two CO dehydrogenases can function in vivo in both directions (60,61).…”

sRNA41 affects ribosome binding sites within polycistronic mRNAs in Methanosarcina mazei Gö1

“…S6), a similar regulation can be expected in other Methanosarcina species. Similarly, for Methanosarcina acetivorans containing two operons encoding ACDS it has been shown that substrate dependent regulation occurs beyond transcriptional regulation (Matschiavelli et al ., ), which is most likely due to early elongation termination (see above). We assume that the presence of a sRNA 41 homologue in M. acetivorans , also known to fix molecular nitrogen, plays a similar role in nitrogen dependent post‐transcriptional regulation by the sRNA 41 homologue on M. mazei .…”

“…5, Supporting Information Fig. S5A), is known to be transcriptionally regulated in response to substrate availability (i.e., acetate) (Hovey et al, 2005;Anderson et al, 2009;Matschiavelli et al, 2012). Since M. mazei G€ o1 3A requires long adaptation times for growth on acetate, as sole energy and carbon source, methylotrophic growth on methanol under acetate depletion was chosen to evaluate acetate dependent regulation.…”