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Dziewit, L, Oscik, K, Bartosik, D and Radlinska, M (2014) Molecular characterization of a novel temperate sinorhizobium bacteriophage, ФLM21, encoding DNA methyltransferase with CcrM-like specificity. J. Virol. 88:13111-24
ΦLM21 is a temperate phage isolated from Sinorhizobium sp. strain LM21 (Alphaproteobacteria). Genomic analysis and electron microscopy suggested that ΦLM21 is a member of the family Siphoviridae. The phage has an isometric head and a long noncontractile tail. The genome of ΦLM21 has 50,827 bp of linear double-stranded DNA encoding 72 putative proteins, including proteins responsible for the assembly of the phage particles, DNA packaging, transcription, replication, and lysis. Virion proteins were characterized using mass spectrometry, leading to the identification of the major capsid and tail components, tape measure, and a putative portal protein. We have confirmed the activity of two gene products, a lytic enzyme (a putative chitinase) and a DNA methyltransferase, sharing sequence specificity with the cell cycle-regulating methyltransferase (CcrM) of the bacterial host. Interestingly, the genome of Sinorhizobium phage ΦLM21 shows very limited similarity to other known phage genome sequences and is thus considered unique.
Bacteriophages/enzymology; Bacteriophages/genetics; Bacteriophages/isolation & purification; Bacteriophages/ultrastructure; DNA, Viral/chemistry; DNA, Viral/genetics; Genome, Viral; Mass Spectrometry; Molecular Sequence Data; Open Reading Frames; Sequence Analysis, DNA; Sinorhizobium/virology; Siphoviridae/enzymology; Siphoviridae/genetics; Siphoviridae/isolation & purification; Siphoviridae/ultrastructure; Site-Specific DNA-Methyltransferase (Adenine-Specific)/genetics; Site-Specific DNA-Methyltransferase (Adenine-Specific)/metabolism; Substrate Specificity; Viral Proteins/chemistry; Viral Proteins/isolation & purification; Virion/ultrastructure
|Gene product||Qualifier||GO Term||Evidence Code||with/from||Aspect||Extension||Notes||Status|
|GO:0009007: site-specific DNA-methyltransferase (adenine-specific) activity||
A sequence comparison with two other phages, Rhizobium gallicum (92% identity) and Sinorhizobium medicae (79% identity), showed that ORF27 encodes an N-6 DNA methyltransferase.
To prove the ORF27 gene product is a methyltransferase, researchers used ORF27 to methylate phage lambda DNA and assessed whether it could be digested by restriction enzymes (Figure 4).
A radioactive methylation assay then showed that the DNA methyltransferase did not methylate other substrates. These findings are consistent with results found from other DNA methyltransferase experiments (Table 3).
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