THE BETA-SUBUNIT RIF-CLUSTER-I IS ONLY ANGSTROMS AWAY FROM THE ACTIVE-CENTER OF ESCHERICHIA-COLI RNA-POLYMERASE

Ribonucleotide analogs bound in the initiating site of Escherichia col i RNA polymerase-promoter complex were cross-linked to the beta subuni t. Using limited proteolysis and chemical degradation, the cross-link was mapped to a segment of beta between amino acids Val(516) and Arg(5 40). This region (Rif-cluster I) is known to harbor many rifampicin-re sistant (Rif(R)) mutations. The results demonstrate that Rif-cluster I is part of the ''5'-face'' of the active center and provide structura l basis for the long-known effects of Rif(R) mutations on transcriptio n initiation, elongation, and termination.