Nucleic Acids Research, 2002, Vol. 30, No. 17 3839-3847
© 2002 Oxford University Press
Functional analysis of iceA1, a CATG-recognizing restriction endonuclease gene in Helicobacter pylori
1 Department of Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA, 2 New England Biolabs, Inc., Beverly, MA 01915, USA, 3 Delft Diagnostic Laboratory, Delft, The Netherlands, 4 Division of Infectious Diseases, Department of Medicine, Vanderbilt University School of Medicine and 5 Department of Medicine and Microbiology, New York University School of Medicine, New York, NY 10016, USA
*To whom correspondence should be addressed at: New York University School of Medicine, 550 First Avenue, New York, NY 10016, USA. Tel: +1 212 263 6394; Fax: +1 212 263 7700; Email: martin.blaser{at}med.nyu.edu
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.
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