[Interaction of DNA and RNA ligases of phage T4 with Cibacron Blue F 3GA]

Using kinetic methods and differential spectrophotometry, the interaction between DNA and RNA ligases T4 and cibacron blue F3GA was studied. It was shown that the dye inhibits the first step of the enzymatic reaction, i. e. the formation of the AMP ligase complex. A 50% inhibition of the AMP-ligase complex by DNA ligase occurs at the dye concentration of 1 X 10(-5) M, that by RNA ligase--at 1 X 10(-4) M. Cibacron blue F3GA also inhibits the formation of end products of the reaction catalyzed by these enzymes. The dye is a noncompetitive inhibitor of RNA ligase with respect to [32P]oligoA20 and a competitive one with respect to ATP. Using differential spectrophotometry, it was found that the interaction occurs predominantly via electrostatic bonds between the SH-groups of the dye and the amino groups of lysine residues. DNA ligase possesses a higher affinity for the dye than RNA ligase.