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Methanogenic Archaea, Methanobacterium, coenzyme F420, F420-dependent N5,N10-methylenetetrahydromethanopterin reductase, methanogenic genes
Abstract:
The gene encoding the F420-dependent N5,N10-methylenetetrahydromethanopterin reductase (Mer), which catalyzes an intermediate step in methanogensis, was cloned and sequenced from the thermophilic Methanobacterium thermoautotrophicum strain Marburg. The gene was identified on a 3.8-kbp BamHI fragment of M. thermoautotrophicum genomic DNA using a homologous probe. The mer gene encoded an acidic protein of 321 amino acids, corresponding to a calculated molecular mass of 33 492 Da. Sequence analysis revealed the presence of a ribosome binding site, a putative promoter, and a possible terminator structure. The size of the mer mRNA was estimated as 1 kb indicating monocistronic transcription. The mer gene was expressed in Escherichia coli yielding an active enzyme of 36 kDa consistent with the apparent molecular mass described for the enzyme from M. thermoautotrophicum. Sequence comparisons revealed similarities between the F420-dependent N5,N10-methylenetetrahydromefhanopterin reductase and a F420-dependent reductase involved in lincomycin biosynthesis in Streptomyces lincolnensis.
