Detection of nucleoside triphosphate binding sites of two types in Escherichia coli RNA-polymerase by affinity labeling

The affinity labeling of E. coli RNA polymerase by periodate-oxidized uridin triphosphate (o-UTP) has been carried out under the conditions of poly(dA) and poly(dT) transcription. The extent of RNA polymerase labeling proved to be 2.5 times higher under the transcription of poly(dA) as compared to poly(dT). The amount of o-UTP attached to beta beta'-subunits has been found to decrease if RNA polymerase is labeled in the transcribed complex with poly(dT). These results as well as those obtained in our previous study (1), suggest that there are two types of binding sites for nucleoside triphosphates and their analogs in E. coli RNA polymerase.