ABSTRACT
The temperate B.subtilis phages phi 3T and rho 11s code, in addition to the multispecific DNA (cytosine-C5) methyltransferases (C5-MTases) M. phi 3TI and M. rho 11sI, which were previously characterized, for the identical monospecific C5-MTases M. phi 3TII and M. rho 11sII. These enzymes modify the C of TCGA sites, a novel target specificity among C5-MTases. The primary sequence of M. phi 3TII (326 amino acids) shows all conserved motifs typical of the building plan of C5-MTases. The degree of relatedness between M. phi 3TII and all other mono- or multispecific C5-MTases ranges from 30-40% amino acid identity. Particularly M. phi 3TII does not show pronounced similarity to M. phi 3TI indicating that both MTase genes were not generated from one another but were acquired independently by the phage. The amino terminal part of the M. phi 3TII (preceding the variable region 'V'), which predominantly constitutes the catalytic domain of the enzyme, exhibits pronounced sequence similarity to the amino termini of a family of A-N6-MTases, which--like M.TaqI--recognize the general sequence TNNA. This suggests that recently described similarities in the general three dimensional organization of C5- and A-N6-MTases imply divergent evolution of these enzymes originating from a common molecular ancestor.
Subject(s)
Bacillus Phages/enzymology , DNA (Cytosine-5-)-Methyltransferases/chemistry , Genes, Viral/genetics , Sequence Homology, Amino Acid , Site-Specific DNA-Methyltransferase (Adenine-Specific)/chemistry , Viral Proteins/chemistry , Viral Structural Proteins/genetics , Amino Acid Sequence , Bacillus Phages/genetics , Bacillus subtilis/virology , Base Sequence , Conserved Sequence , DNA (Cytosine-5-)-Methyltransferases/genetics , DNA (Cytosine-5-)-Methyltransferases/metabolism , DNA, Viral/metabolism , Methylation , Molecular Sequence Data , RNA, Messenger/biosynthesis , RNA, Viral/biosynthesis , Restriction Mapping , Sequence Alignment , Sequence Analysis, DNA , Site-Specific DNA-Methyltransferase (Adenine-Specific)/genetics , Site-Specific DNA-Methyltransferase (Adenine-Specific)/metabolism , Substrate Specificity , Viral Proteins/genetics , Viral Proteins/metabolismABSTRACT
The temperate B.subtilis phages phi 3T and rho 11s code, in addition to the multispecific DNA (cytosine-C5) methyltransferases (C5-MTases) M.phi 3TI and M.rho 11sI, which were previously characterized, for the identical monospecific C5-MTases M.phi 3TII and M.rho 11sII. These enzymes modify the C to TCGA sites, a novel target specificity among C5-MTases. The primary sequence of M.phi 3TII (326 amino acids) shows all conserved motifs typical of the building plan of C5-MTases. The degree of relatedness between M.phi 3TII and all other mono- or multispecific C5-MTases ranges from 30-40% amino acid identity. Particularly M.phi 3TII does not show pronounced similarity to M.phi 3TI indicating that both MTase genes were not generated from one another but were acquired independently by the phage. The amino terminal part of the M.phi 3TII (preceding the variable region 'V'), which predominantly constitutes the catalytic domain of the enzyme, exhibits pronounced sequence similarity to the amino termini of a family of A-N6-MTases, which--like M.Taql--recognize the general sequence TNNA. This suggests that recently described similarities in the general three dimensional organization of C5- and A-N6-MTases imply divergent evolution of these enzymes originating from a common molecular ancestor.
Subject(s)
Bacillus Phages/enzymology , DNA (Cytosine-5-)-Methyltransferases/chemistry , Genes, Viral/genetics , Sequence Homology, Amino Acid , Site-Specific DNA-Methyltransferase (Adenine-Specific)/chemistry , Viral Proteins/chemistry , Viral Structural Proteins/genetics , Amino Acid Sequence , Bacillus Phages/genetics , Bacillus subtilis/virology , Base Sequence , Conserved Sequence , DNA (Cytosine-5-)-Methyltransferases/genetics , DNA (Cytosine-5-)-Methyltransferases/metabolism , DNA, Viral/metabolism , Methylation , Molecular Sequence Data , RNA, Messenger/biosynthesis , RNA, Viral/biosynthesis , Restriction Mapping , Sequence Alignment , Sequence Analysis, DNA , Site-Specific DNA-Methyltransferase (Adenine-Specific)/genetics , Site-Specific DNA-Methyltransferase (Adenine-Specific)/metabolism , Substrate Specificity , Viral Proteins/genetics , Viral Proteins/metabolismABSTRACT
The DNA methyltransferase (Mtase) genes of temperate Bacillus subtilis phages SPR, phi 3T, SP beta and rho 11 can be transferred by transfection and recombination to the genome of the related non-modifying phage Z. Integration of the Mtase genes occurs in phage Z DNA at a unique location which is homologous with the flanking regions of the Mtase genes of the related phages. In lysogenic cells carrying recombinant phages, expression of the Mtase genes is repressed, irrespective of whether the Mtase genes were derived from phage donors which were homo- or heteroimmune to phage Z.
