tailieunhanh - Báo cáo khoa học: Characterization of an N6 adenine methyltransferase from Helicobacter pylori strain 26695 which methylates adjacent adenines on the same strand

Genomic sequences ofHelicobacter pyloristrains 26695, J99, HPAGI and G27 have revealed an abundance of restriction and modification genes. hp0050, which encodes an N 6 adenine DNA methyltransferase, was cloned, overexpressed and purified to near homogeneity. | ễFEBS Journal Characterization of an N6 adenine methyltransferase from Helicobacter pylori strain 26695 which methylates adjacent adenines on the same strand Ritesh Kumar1 Asish K. Mukhopadhyay2 and Desirazu N. Rao1 1 Department of Biochemistry Indian Institute of Science Bangalore India 2 Division of Bacteriology NationalInstitute of Cholera and Enteric Disease Kolkata India Keywords base flipping DNA methyltransferase Helicobacter pylori S-adenosyl-L-methionine site-directed mutagenesis Correspondence D. N. Rao Department of Biochemistry Indian Institute of Science Bangalore 560 012 India Fax 91 80 2360 814 Tel 91 80 2293 2538 E-mail dnrao@ Received 18 November 2009 revised 26 December 2009 accepted 25 January 2010 doi Genomic sequences of Helicobacter pylori strains 26695 J99 HPAGI and G27 have revealed an abundance of restriction and modification genes. hp0050 which encodes an N6 adenine DNA methyltransferase was cloned overexpressed and purified to near homogeneity. It recognizes the sequence 5 -GRRG-3 where R is A or G and most intriguingly methylates both adenines when R is A 5 -GAAG-3 . Kinetic analysis suggests a nonpro-cessive repeated-hit mechanism of methylation in which HP0050 methyltransferase methylates one adenine at a time in the sequence 5 -GAAG-3 . This is the first report of an N6 adenine DNA methyltransferase that methylates two adjacent residues on the same strand. Interestingly HP0050 homologs from two clinical strains of H. pylori PG227 and 128 methylate only 5 -GAGG-3 compared with 5 -GRRG-3 in strain 26695. HP0050 methyltransferase is highly conserved as it is present in more than 90 of H. pylori strains. Inactivation of hp0050 in strain PG227 resulted in poor growth suggesting its role in the biology of H. pylori. Collectively these findings provide impetus for exploring the role s of this conserved DNA methyltransferase in the cellular processes of H. pylori. Introduction DNA .

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