title: Organization and sequence of the hsd genes of Escherichia coli K-12.
abstract: The nucleotide sequence of the hsdR and M genes, together with that for hsdS comprises an 8400 base segment spanning the entire hsd region of Escherichia coli K-12. The three hsd genes are transcribed in the same direction, but from two promoters. hsdR and hsdM are separated by 492 base-pairs, whereas the termination codon of hsdM overlaps the initiation codon of hsdS. pres precedes hsdR, and our data indicate a transcription termination signal in the interval between hsdR and pmod, as expected if transcription of hsdM and S is dependent on pmod. Transcription from pres is not influenced by the products of the hsdM and S genes, and the mechanism whereby restriction is prevented when the hsd region is transferred to a modification-deficient cell remains to be elucidated. A segment of the predicted amino acid sequence of the M polypeptide shares homology with a variety of adenine methylases and may identify part of the active site for methylation of specific adenine residues. The R polypeptide shows homology with a variety of ATPases, and pronounced regions of alpha-helical structure are predicted, one of which is amphipathic.
authors.affiliation: Department of Molecular Biology, University of Edinburgh, Scotland.
authors.forename: W A
authors.initials: WA
authors.lastname: Loenen
authors.forename: A S
authors.initials: AS
authors.lastname: Daniel
authors.forename: H D
authors.initials: HD
authors.lastname: Braymer
authors.forename: N E
authors.initials: NE
authors.lastname: Murray
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D004926:Escherichia coli / Q000235:genetics*; D005798:Genes, Bacterial; D008780:Methyltransferases; D008969:Molecular Sequence Data; D014176:Protein Biosynthesis; D012689:Sequence Homology, Nucleic Acid; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific); D013728:Terminator Regions, Genetic; D014158:Transcription, Genetic
chemical_list: D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D008780:Methyltransferases; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific)