[Methyl-cytosine specific restriction in Escherichia coli K-12]. / Izuchenie metil-tsitozin spetsificheskoi restriktsii u Escherichia coli K-12.

Experiments on transformation of Escherichia coli K-12 cells by plasmids carrying RM systems with different recognition sites containing 5-methylcytosine have shown that the gene mcrB determines the function of restriction. The data obtained made it possible to believe that E. coli possesses no restriction system recognizing specifically cytosine methylated in position 4.

[Cloning of the restriction-modification genes of Bacillus centrosporus in Escherichia coli]. / Klonirovanie genov restriktsii-modifikatsii Bacillus centrosporus v Escherichia coli.

A genomic library of Bacillus centrosporus was obtained using pBR327 as a vector. The total plasmid DNA of the library was cleaved by the BcnI restriction endonuclease and then transformed in Escherichia coli RR1. Two clones possessing restriction and DNA modification profiles of BcnI were identified among the transformants. Their respective plasmids were 13.3 and 9.05 kbp in size. Restriction mapping of both plasmids showed each of them to contain two sites for HindIII and one for both Eco31I and Eco47III, located at the same distance. This was assumed to be the location region of the BcnI restriction-modification genes. Confirmation of the assumption was obtained by deletion mapping of the recombinant plasmids. Special features concerning cloning of the restriction-modification genes are discussed on the basis of the results obtained.