INTERACTION OF T4 PHAGE DNA-[N6-ADENINE]-METHYLTRANSFERASE WITH SUBSTRATES CONTAINING DEFECTIVE RECOGNITION SITES

The effect of the structure of recognition site GATC in a substrate du plex on its complexation with DNA-[N6-adenine]-methyltransferase of T4 phage (T4 MTase) was studied. The pel retardation method was employed to reveal the complexes. As compared with the native duplexes, the ma jority of defective duplexes had the same or even better affinity to T 4 MTase; however, no correlation was found between the complex stabili ty and effectiveness of the duplexes as substrates for methylation. Ap parently, formation of a stable enzyme-DNA complex does not require co ntinuity of the two strands of the duplex and perfect base pairing in the recognition site. A half of the constituents of the recognition si te suffices for stable complexes with T4 MTase to form. Deoxyguanosine residues in both strands of the modified GATC are shown to be indispe nsable for complex formation.