Purification of the novel endonuclease, Hpy188I, and cloning of its restriction-modification genes reveal evidence of its horizontal transfer to the Helicobacter pylori genome.
We have isolated a novel restriction endonuclease, Hpy188I, from Helicobacter pylori strain J188. Hpy188I recognizes the unique sequence, TCNGA, and cleaves the DNA between nucleotides N and G in its recognition sequence to generate a one-base 3' overhang. Cloning and sequence analysis of the Hpy188I modification gene in strain J188 reveal that hpy188IM has a 1299-base pair (bp) open reading frame (ORF) encoding a 432-amino acid product. The predicted protein sequence of M.Hpy188I contains conserved motifs typical of aminomethyltransferases, and Western blotting indicates that it is an N-6 adenine methyltransferase. Downstream of hpy188IM is a 513-bp ORF encoding a 170-amino acid product, that has a 41-bp overlap with hpy188IM. The predicted protein sequence from this ORF matches the amino acid sequence obtained from purified Hpy188I, indicating that it encodes the endonuclease. The Hpy188I R-M genes are not present in either strain of H. pylori that has been completely sequenced but are found in two of 11 H. pylori strains tested. The significantly lower G + C content of the Hpy188I R-M genes implies that they have been introduced relatively recently during the evolution of the H. pylori genome.
Xu
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Department of Microbiology and Immunology, Division of Infectious Diseases, Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
Stickel
S
S
Roberts
R J
RJ
Blaser
M J
MJ
Morgan
R D
RD
D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers; D015252:Deoxyribonucleases, Type II Site-Specific / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D022761:Gene Transfer, Horizontal; D016680:Genome, Bacterial; D016480:Helicobacter pylori / Q000235:genetics*; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D013379:Substrate Specificity
D017931:DNA Primers; C410411:endodeoxyribonuclease Hpy188I; D015252:Deoxyribonucleases, Type II Site-Specific