Reaction of 5-diazonium-1-H-tetrazole with histidine and tyrosine residues and RNA polymerase from Escherichia coli B

Abstract

1. 1.5-Diazonium-1-H-tetrazole (DHT) reacts rapidly with Escherichia coli RNA polymerase (nucleoside triphosphate:RNA nucleotidyltransferase, EC 2.7.7.6). histidine, histamine, N-acetyltyrosine ethyl ester but slowly with tyrosine. 2. 2.Simultaneous equations incorporating ε (476 nm) and ε (548 nm) resolved the overlapping spectra of the bisazo derivatives of histidine and tyrosine, and when applied to RNA polymerase indicated that 90% (54 residues) of histidine and 33% (33 residues) of the tyrosine are on or near the surface of the molecule. 3. 3.The AMP-incorporating activity of RNA polymerase decreased in a parallel fashion to the reaction of the first histidine and tyrosine residues with DHT, and exponentially on photooxidation with Rose Bengal. 4. 4.The competitive inhibitor 9-aminoacridine as well as rifampicin partially protected the enzyme from inactivation by DHT whereas DNA and 1,2,3,4-tetrahydro-9-aminoacridine (non-inhibitory) did not.