Kinetic characterization of the EcaI methyltransferase

László SZILÁK, András DÉR, Ferenc DEÁK, Pál VENETIANER

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A kinetic analysis of the EcaI adenine‐N6‐specific methyltransferase (MTase) is presented. The enzyme catalyzes the transfer of a methyl group from S‐adenosyl‐L‐methionine (AdoMet) to the adenine of the GGTNACC sequence with a random rapid‐equilibrium mechanism. Experiments with a synthetic, 14‐bp DNA substrate suggest that recognition of the specific site of DNA occurs after the binding of AdoMet. Proton concentration does not affect the dissociation constant of AdoMet while Vm and the dissociation constant of DNA show a maximum around pH 8. Increasing the amount of S‐adenosyl‐L‐homocysteine decreases the inhibitory effect of methylated DNA which proves the active role of AdoMet in site recognition. Experiments with hemimethylated DNA show that the methylase binds the double‐stranded DNA asymmetrically.

Original languageEnglish
Pages (from-to)727-733
Number of pages7
JournalEuropean Journal of Biochemistry
Issue number2
Publication statusPublished - Dec 1993


ASJC Scopus subject areas

  • Biochemistry

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