J. Biol. Chem., Vol. 265, Issue 11, 6086-6091, Apr, 1990
Primary structure of a DNA (N6-adenine)-methyltransferase from Escherichia coli virus T1. DNA sequence, genomic organization, and comparative analysis
E Schneider-Scherzer, B Auer, EJ de Groot and M Schweiger
Institut fur Biochemie, Universitat Innsbruck, Austria.
Escherichia coli virus T1 encodes a DNA (N6-adenine)-methyltransferase
(M.T1) with the same sequence specificity as the E. coli DNA (N6-
adenine)-methyltransferase (M.Eco dam). This enzyme was purified to
homogeneity and a partial amino acid sequence determined. Oligonucleotides
were constructed and used not only as probes to map the gene on the T1
genome, but also as primers in sequencing reactions to establish the
nucleotide sequence of the M.T1 locus by primer extension. These data
represent the first analysis of the genomic organization of bacterial virus
T1 on a molecular level. Significant homology to E. coli consensus
transcription and translation-initiation signals suggest that the gene for
M.T1 is most probably under control of its own promoter. It may be
transcribed as a polycistronic mRNA, together with a downstream open
reading frame which codes for a polypeptide containing 83 amino acids (HP
83). Both the deduced primary and the secondary structure of the M.T1 were
compared to those of other known DNA methyltransferases, especially those
recognizing the sequence, GATC; there is little similarity of the T1 enzyme
to the other members of this family.