INHIBITORS OF ESCHERICHIA-COLI RNA-POLYMERASE SPECIFIC FOR THE SINGLE-STRANDED-DNA OF TRANSCRIPTION INTERMEDIATES - TETRAHEDRAL CUPROUS CHELATES OF 1,10-PHENANTHROLINES

Single-stranded DNA of the lacUV-5 promoter formed at the active site of Escherichia coli RNA polymerase during transcription is specificall y cleaved by the redox active tetrahedral cuprous chelates of 1,10-phe nanthroline and its derivatives. The cleavage sites are observed in th e open, initiating, and elongating complexes. Redox-inert, tetrahedral cuprous chelates of neocuproine (2,9-dimethyl-1, 10-phenanthroline) a nd its 5-phenyl and 4-phenyl derivatives protect the template strand o f DNA from scission within these steady state intermediates and inhibi t transcription. Although these cuprous chelates of neocuproine bind a t multiple sites within three distinct enzyme intermediates, the highe st affinity site is within the elongation complex. The I-50 of 5 mu M for the 2:1 5-phenylneocuproine cuprous complex ((S phi NCCu+) in runo ff transcription therefore primarily reflects its interaction with thi s intermediate. The neocuproine cuprous chelates are novel transcripti on inhibitors because they bind to single-stranded DNA sites generated during the course of catalysis by RNA polymerase.