The restriction endonucleases in Bacillus amyloliquefaciens N strain. Substrate specificities

Abstract

Two species of restriction endonuclease were isolated by gel filtration and DEAE-cellulose chromatography from a cell-free extract of Bacillus amyloliquefaciens (B. subtilis) N strain; a lower molecular weight endonuclease (endo-nuclease R BamNI) and a higher molecular-weight one (endonuclease R. Bam-Nx). Both of them required only Mg 2+ for their activities. Endonuclease R. Bam-Nx introduced a larger number of site-specific scissions in Escherichia coli phage γ DNA than endonuclease R. BamNI did. Endonuclease R. BamNx cleaved Bacillus phage ø105C DNA at the specific sites which are classified into two groups: one type of sites is modified by B. amyloliquefaciens H strain in vivo while the other is not affected. It was also active on DNAs of E. coli phage T7, λdvl, Simian virus 40 (SV40) and colicinogenic factor ColEl and was inactive on DNAs of Bacillus phages ø29 and M2. Endonuclease R. BamNI cleaved DNA in the same nucleotide sequences as endonuclease R. BamHI isolated from H strain by Wilson and Young. This endonuclease was active on DNAs of phage λ, λdvl and SV40, and was inactive on DNAs of phages ø105C, ø29, M2 and T7, and ColEI DNA.