Structure and sequence divergence of two archaebacterial genes.

Abstract

The DNA sequences of a region that includes the hisA gene of two related methanogenic archaebacteria, Methanococcus Methanogens are members of the archaebacteria, a group of prokaryotic organisms exhibiting several properties that are distinct from those seen in either eubacteria or eukaryotes (1, 2). Therefore, it was somewhat surprising when it was found that DNA cloned from several methanogenic species could complement auxotrophic mutations in Escherichia coli, Bacillus subtilis (3-6), and Salmonella typhimurium (unpublished results). In the case of two methanogens of the genus Methanococcus (vannielii and voltae), it was possible to clone methanogen DNA that complemented the hisA mutation of E. coli (4, 6). Since the hisA-complementing activity was efficiently expressed regardless of the orientation of the cloned DNA fragment within the vector, it seemed likely that the methanogen DNA harbored sequences that were recognized as signals for both transcription and translation. That methanococcal DNA would contain signals for initiation ofan early step in translation in E. coli was expected because these methanococci have the sequence A-U-C-A-C-C-U-C-C at the 3' end of their 16S rRNA (1), which is similar to that found at the 3' end of E. coli 16S rRNA (7). This sequence is believed to be important for initial binding of ribosomes to mRNA molecules (8).Since both M. voltae and M. vannielii have an overall base composition of --70% A+T (1), they should statistically contain those high A+T-rich sequences that often function as promoters in prokaryotes. Whether similar A+T-rich sequences are used as promoters for recognition by methanogen DNA-dependent RNA polymerases is currently unknown. The subunit composition of RNA polymerases from archaebacteria more closely resembles eukaryotic RNA polymerase II than eubacterial RNA polymerase (9), and thus archaebacterial promoters may well be eukaryotic rather than prokaryotic in their sequence organization.To better understand the molecular basis for expression of the hisA-complementing methanogen genes in E. coli and to provide basic information for evaluating possible mechanisms of gene expression in methanogens, we have sequenced the hisA-complementing genes ofboth M. voltae and M. vannielfi. The sequences obtained indicate evolutionary divergence of archaebacterial structural genes, support the prediction ofribosomal binding sites, and demonstrate repetitive elements within the intergenic regions. MATERIALS AND METHODSBacterial Strains and Phage. E. coli K-12 strain X760, which is a hisA auxotroph (4), was used to determine if plasmid derivatives carried hisA-complementing DNA.Enzymes and Chemicals. Restriction enzymes were purchased from Bethesda Research Laboratories, BoehringerMannheim, or New England Biolabs and were used in accordance with the supplier's directions. Klenow DNA polymerase, T4 DNA ligase, and proteinase K were purchased from Boehringer Mannheim. Deoxy and dideoxynucleotide triphosphates were purchased from Pharmacia and P-L Biochemicals. ...

Conservation of structure in the human gene encoding argininosuccinate synthetase and the argG genes of the archaebacteria Methanosarcina barkeri MS and Methanococcus vannielii

“…2 and 3). Intergenic regions in methanogens frequently contain multiple copies of both direct and inverted repeat sequences (3,4,22,27), and this is also the case in the intergenic regions preceding the argG genes. In Methanosarcina barkeri MS, there are six tandem copies of a 14-bp direct repeat immediately 3' to the upstream ORF, Fig.…”

“…Several genes have been cloned from methanogenic archaebacteria by their ability to complement auxotrophic mutations in Escherichia coli (1, 4,12,18,22,27,29). One of the first genes cloned from Methanosarcina barkeri MS was shown to complement mutations in the argG locus of E. coli and was therefore designated as the argG gene of Methanosarcina barkeri MS (12).…”

Identification of a eukaryotic‐like protein kinase gene in Archaebacteria

“…To better characterize these sequences, we have obtained from the authors (C. Weil & G. Beckler; see Cue et al, 1985;Weil et al, 1987) two unpublished sequences, the complete sequence of ORF547 and a partial sequence of the orthologous ORF in Methanococcus therrnolithotrophicus, ORF I14 (see Fig. 1).…”

Cloning and characterization of the methyl coenzyme M reductase genes from Methanobacterium thermoautotrophicum

“…The DNA sequences flanking the highly expressed MCR genes should contain strong transcriptional signals, which are known to be different from their eucaryotic or eubacterial counterparts (8,10,16). We therefore mapped the boundaries of the methanogenic mRNA coding for MCR and could define a transcription terminator.…”