2Novosibirsk State University, ul. Pirogova 2, 630090 Novosibirsk, Russia
3State Research Center of Virology and Biotechnology “Vector”, 630559 Kol’tsovo, Novosibirsk Region, Russia
* To whom correspondence should be addressed.
Received May 20, 2010; Revision received June 22, 2010
A restriction–modification system from Bacillus psychrodurans AC (recognition sequence 5′-CCGC-3′) comprises two DNA methyltransferases: M1.BspACI and M2.BspACI. The bspACIM1 gene was cloned in the pJW2 vector and expressed in Escherichia coli cells. High-purity M1.BspACI preparation has been obtained by chromatography on different carriers. M1.BspACI has a temperature optimum of 30ºC and demonstrates maximum activity at pH 8.0. M1.BspACI modifies the first cytosine in the recognition sequence 5′-CCGC-3′. The kinetic parameters of M1.BspACI DNA methylation are as follows: Km for phage λ DNA is 0.053 µM and Km for S-adenosyl-L-methionine is 5.1 µM. The catalytic constant (kcat) is 0.095 min–1.
KEY WORDS: DNA methyltransferase, Bacillus psychrodurans, enzyme kinetics