Functional analysis of iceA1, a CATG‐recognizing restriction endonuclease gene in Helicobacter pylori

• Published in: Nucleic acids research 2002-09, Vol.30 (17), p.3839-3847
• Main Authors: Xu, Qing, Morgan, R. D., Roberts, R. J., Xu, S. Y., van Doorn, L. J., Donahue, J. P., Miller, G. G., Blaser, Martin J.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Base Sequence; Deoxyribonucleases, Type II Site-Specific - genetics; Deoxyribonucleases, Type II Site-Specific - metabolism; DNA Restriction Enzymes - genetics; DNA Restriction Enzymes - metabolism; DNA, Bacterial - chemistry; DNA, Bacterial - genetics; Escherichia - genetics; Frameshift Mutation - genetics; Helicobacter pylori - enzymology; Helicobacter pylori - genetics; Molecular Sequence Data; Neisseria - enzymology; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; Sequence Analysis, DNA; Sequence Homology, Nucleic Acid
• ISSN: 0305-1048; 1362-4962; 1362-4962
• DOI: 10.1093/nar/gkf504

iceA1 in Helicobacter pylori is a homolog of nlaIIIR, which encodes the CATG‐specific restriction endonuclease NlaIII in Neisseria lactamica. Analysis of iceA1 sequences from 49 H.pylori strains shows that a full‐length NlaIII‐like ORF is present in 10 strains, including CH4, but in other strains, including strain 60190, the ORFs are truncated due to a variety of mutations. Our goal was to determine whether iceA1 can encode a NlaIII‐like endonuclease. Overexpression in Escherichia coli of iceA1 from CH4, but not from 60190, yielded NlaIII‐like activity, indicating that the full‐length iceA1 is a functional endonuclease gene. Repair of the iceA1 frameshift mutation in strain 60190 and its expression in E.coli yielded functional NlaIII‐like activity. We conclude that iceA1 in CH4 is a functional restriction endonuclease gene, while iceA1 in 60190 is not, due to a frameshift mutation, but that its repair restores its restriction endonuclease activity.