The role of uncharacterized methyl-x:coenzyme M methyltransferases for activation of novel methylotrophic energy substrates in Methanosarcina acetivorans

点击翻译按钮获取中文摘要

Methanogenic archaea are responsible for most of the biologically produced methane. This process, methanogenesis, plays a critical role in the carbon cycle, global warming, alternative energy strategies, waste treatment and agriculture. Methanosarcina species have a comparably broad substrate spectrum and are able to utilize H2+CO2, carbon monoxide, acetate, and methylated compounds for energy conservation. During the latter, called methylotrophic methanogenesis, methylated compounds enter the methanogenic pathway via activation by substrate-specific methyltransferases, which transfer the methyl group to coenzyme M (CoM). The genome of the model methanogen Methanosarcina acetivorans encodes several uncharacterized methyl-x:coenzyme M methyltransferases (xMTs) lending to the hypothesis that the organism’s methylotrophic capacity exceeds the known one. Of numerous potential substrates tested some methoxylated compounds supported growth and were metabolized via the methanol-specific pathway, which leaves the question as to the role of the xMTs still open. In the second grant period, co-metabolism of those and other methyl-containing compounds will be analyzed to assess the role of the xMTs, the potential environmental relevance of substrate turnover, and the substrate range of the methyltransferase systems for methanol, methylamines and methylsulfides. Furthermore, biochemical analysis of dimethylsulfide activation -down to the atomic level- will provide detailed insights in the metabolism of environmentally important volatile sulfur species. The many methyltransferases encoded in Methanosarcina are paradigmatic for their specious genetic redundancy and promise novel insights into the metabolic versatility of these important organisms.