Posttranslational Methylation of Arginine in Methyl Coenzyme M Reductase Has a Profound Impact on both Methanogenesis and Growth of <em>Methanococcus maripaludis</em>

Catalyzing the key step for anaerobic production and/or oxidation of methane and likely other short-chain alkanes, methyl coenzyme M reductase (Mcr) and its homologs play a key role in the global carbon cycle. The McrA subunit possesses up to five conserved posttranslational modifications (PTMs) at its active site. It was previously suggested that methanogenesis marker protein 10 (Mmp10) could play an important role in methanogenesis. To systematically examine its physiological role, in this work, mmpX (locus tag MMP1554), the gene encoding Mmp10 in Methanococcus maripaludis, was deleted with a new genetic tool, resulting in the complete loss of the 5-C-(S)-methylarginine PTM of residue 275 in the McrA subunit. When the ΔmmpX mutant was complemented with the wild-type gene expressed by either a strong or a weak promoter, methylation was fully restored. Compared to the parental strain, maximal rates of methane formation by whole cells were reduced by 40 to 60% in the ΔmmpX mutant. The reduction in activity was fully reversed by the complement with the strong promoter. Site-directed mutagenesis of mmpX resulted in a differential loss of arginine methylation among the mutants in vivo, suggesting that activities of Mmp10 directly modulated methylation. R²⁷⁵ was present in a highly conserved PXRR²⁷⁵(A/S)R(G/A) signature sequence in McrAs. The only other protein in M. maripaludis containing a similar sequence was not methylated, suggesting that Mmp10 is specific for McrA. In conclusion, Mmp10 modulates the methyl-Arg PTM on McrA in a highly specific manner, which has a profound impact on Mcr activity.. Authors: Lyu, Zhe [Univ. of Georgia, Athens, GA (United States); University of Georgia]; Shao, Nana [Univ. of Georgia, Athens, GA (United States)]; Chou, Chau-Wen [Univ. of Georgia, Athens, GA (United States)]; Shi, Hao [Univ. of Georgia, Athens, GA (United States)]; Patel, Ricky [Univ. of Georgia, Athens, GA (United States)]. DOE Contract: SC0018028. Subjects: 03 NATURAL GAS; 09 BIOMASS FUELS; 59 BASIC BIOLOGICAL SCIENCES; 60 APPLIED LIFE SCIENCES; Methanococcus; coenzyme M methylreductase; post-translational modification; radical SAM enzyme