Complexes of DNA-[N6-adenine]-methyltransferases of T-even phages with their substrates which are determined by "blocking in gel" method
Petrov, N.A.; Gorbunov, I.A.; Naumochkin, A.N.; Malygin, E.G.
Molekuliarnaia Biologiia 31(6): 966-972
1997
ISSN/ISBN: 0026-8984 PMID: 9480432 Document Number: 478401
DNA-(N6-adenine)-methyltransferases of T4 and T2 phages (T4- and T2-MTases) (E.C. 2.1.1) recognize in double-stranded DNA palindrome GATC site and catalyze the transfer of the methyl group from S-adenosyl-L-methionine (SAM) to position N6 of the adenine residue. The "gel retardation" method was used to study the relative effectiveness of complex formation of T4- and T2-MTases with oligonucleotide substrates of varying length containing GATC in the middle of the duplex. It is shown that T4-MTase forms stable complexes with 20-member duplexes containing a nonmodified or hemimethylated GATC site. The binding of the duplex to T4-MTase is enhanced in the presence of SAM. Parameters of the interaction of SAM with MTase free bound with the 20-member duplex were determined. T2-MTase which has a higher catalytic activity than T4-MTase, forms less stable complexes with oligonucleotides. It is concluded that there is no direct correlation between the stability of the enzyme-substrate complexes and the catalytic activity of the enzymes.