IDENTIFYING INTERACTING REGIONS IN THE BETA-SUBUNIT OF ESCHERICHIA-COLI RNA-POLYMERASE

Numerous physical and genetic approaches have identified residues in t he alpha, beta, beta' and sigma subunits of Escherichia coli RNA polym erase that are involved in transcriptional processes; in contrast, rel atively little data exist to demonstrate interacting regions within or between the subunits themselves. As a means of identifying regions in the beta subunit that may interact, we have sought intragenic suppres sor mutations of a class of elongation-defective and termination-profi cient inviable rpoB alleles that affect highly conserved residues. We obtained intragenic allele-specific suppressors of GD566 (located in c onserved region D) and AV676 (located in conserved region E). With one exception, these allele-specific suppressors also map to highly conse rved regions of the beta subunit. Allele specific suppression is a gen etic criterion for protein-protein interaction. Moreover, the function al properties of the mutants suggests that suppression is likely to re sult from protein-protein interaction rather than from functional comp ensation. Our suppression studies provide evidence for the interaction of conserved regions B and D as well as conserved regions E and H of the beta polypeptide. We suggest that these, as well as other conserve d regions of the beta polypeptide, may interact with each other to pro vide a framework for the function of the enzyme. (C) 1996 Academic Pre ss Limited