||Ohio State Univ., Columbus. ;University of East Anglia, Norwich (England). School of Biological Sciences.;Environmental Protection Agency, Cincinnati, OH. Risk Reduction Engineering Lab.;Department of Energy, Washington, DC.;Gas Research Inst., Chicago, IL.
An analysis of the structure and presumed regulatory signals in sequenced methanogen genes is presented. The evidence for polycistronic transcriptional units is extended by inclusion of a DNA sequence, cloned from Methanobrevibacter smithii, which precedes the M. smithii proC gene. Comparison of DNA sequences indicates that a consensus core ribosome binding sequence for methanogens would be 5' AGGTGA and that many of the ribosome binding sequences are, in fact, longer than the core sequence containing 7 bases with the potential to hybridize to 16SrRNA. The majority, but not all, of the sequenced methanogen genes conform to the rule in which RNY codons (R-purine, Y-pyrimidine, N-purine or pyrimidine) occur most frequently in the translated reading frame. Codon usages by different methanogens reflect the need to accommodate genomes with very different overall %mol G+G contents. Codons such as AUA, AGA, and AGG, rarely used by E. coli are frequently used by methanogens. The dinucleotide, CG, which occurs very infrequently in eucaryotic DNAs is also rarely found in methanogen genes.