Studies on the catalytic center and substrate control of Escherichia coli B DNA-dependent RNA polymerase

Naturally occurring and synthetic nucleosides have been used in this study to examine substrate regulation of RNA polymerase activity and the location and partial structure of the active center of this enzyme. Results have been presented which indicate: (1) the rate of RNA synthesis in vitro can be regulated by the relative concentration ratio of one of its four substrates, ATP; (2) inhibition of RNA synthesis in vitro by ADP does occur in the presence of high substrate concentrations; (3) [superscript 35]S-MMPR-OP can be used as an affinity label and binds only to the ß subunit of the enzyme; (4) inhibition by the 5'-monophosphate of methylmercaptopurine riboside, provides evidence for an α-phosphate binding subsite within the catalytic center of the enzyme.