Use of ATP, dATP and their alpha-thio derivatives to study DNA ligase adenylation

Bacteriophage-T4 and human type I DNA ligases were found capable of self-adenylating upon exposure to both ribo- and deoxyribo-[alpha-35S]thio-ATP. However, the joining reaction does not take place in the presence of the deoxyribotriphosphates. Enzyme adenylation is reversed in all cases by an excess of PPi, but the rate of reversion is lower with thio derivatives. Therefore thio derivatives can be used to study the adenylation of DNA ligases and to search for specific inhibitors of the first step of the ligation reaction. In addition we show that thio derivatives can be used to detect DNA ligase adenylation activity covalently bound to a solid matrix.