Nudeotide sequence of the BsuRI restriction-modification system

Abstract

The genes of the 5'-GGCC specific BsuRI restriction-modification system of Bacillus subtilis have been cloned and expressed in E. coli and their nucleotide sequence has been determined. The restriction and modification genes code for polypeptides with calculated molecular weights of 66,314 and 49,642, respectively. Both enzymes are coded by the same DNA strand. The restriction gene is upstream of the methylase gene and the coding regions are separated by 780 bp. Analysis of the RNA transcripts by S1-nuclease mapping indicates that the restriction and modification genes are transcribed from different promoters. Comparison of the amino acid sequences revealed no homology between the BsuRI restriction and modification enzymes. There are, however, regions of homology between the BsuRI methylase and two other GGCC specific modification enzymes, the BspRI and SPR methylases.

Regulation of the BamHI restriction-modification system by a small intergenic open reading frame, bamHIC, in both Escherichia coli and Bacillus subtilis

“…During the initial cloning of the BamHI system, two subclones of bamHIM, pBamM2.2 and pBamM1.8, were generated (7). The former contained intact bamHIC, whereas in the latter bamHIC was truncated (8 [25,36]) and pSUll (encoding bsuRIM, methylating GGmCCC [19,20]) were selected, since both have been shown to be strongly restricted when transformed into McrBC+ hosts (20,27). bamHIC had no effect on McrBC restriction of the mspIM plasmid; in both the presence and absence of bamHIC, the plasmid was restricted 10,000-fold ( 20).…”

“…Plasmids pBamMl.8 and pBamM2.2 (containing bamHIM [7]), pMspI-30 (containing mspIM [25]), and pSUll (containing bsuRIM [20]) were described previously. Plasmid pBamRM5.0, a pACYC184 derivative containing the complete BamHI RM system on a 5.0-kb HindIII fragment, was used in various subcloning experiments (7).…”

Restriction-modification systems as genomic parasites in competition for specific sequences.

“…Our selfish gene hypothesis suggests that bacteria may have evolved anti-RM systems as their viruses have done. We can think of four possible anti-RM mechanisms: (i) methyl-specific restriction systems (37,38); (ii) methylation by bacterial solo methylases (39), which may protect bacterial chromosomes from postsegregational cleavage by certain RM systems; (iii) homologous recombination (40); and (iv) ligation with DNA ligase (41).…”

Regulation of the pAD1-encoded sex pheromone response in Enterococcus faecalis: nucleotide sequence analysis of traA

“…The deduced protein of traA exhibited weak homology with several DNA-binding proteins: Bacillus subtilis BsuRI restriction enzyme (17% conserved plus 18% identical residues [30] within the first 281 residues of TraA), B. subtilis DNA polymerase III (15% conserved plus 15% identical residues [39]), and T5 DNA polymerase (14% conserved plus 19% identical residues [31] within the first 227 residues of TraA). The homology detected to the latter two proteins was within regions of these proteins predicted to play a role in 3'-*5' exonuclease activity.…”