BIPARTITE FUNCTIONAL MAP OF THE ESCHERICHIA-COLI RNA POLYMERASE-ALPHA SUBUNIT - INVOLVEMENT OF THE C-TERMINAL REGION IN TRANSCRIPTION ACTIVATION BY CAMP-CRP

The alpha-subunit of Escherichia coli RNA polymerase plays a major role in the subunit assembly. Carboxy-terminal deletion derivatives lacking 73 or 94 amino acid residues were assembled in vitro into enzyme molecules. Core enzymes consisting of these C-terminal-truncated alpha-subunits were as active in RNA synthesis as native core enzyme. By the addition of sigma-70 subunit, these mutant enzymes initiated transcription from certain promoters. The mutant RNA polymerases, however, did not show cAMP-CRP activated transcription. These results demonstrate that the N-terminal region of the alpha-subunit is involved in the formation of active enzyme molecule, while the C-terminal region plays an essential role in response to transcription activation by cAMP-CRP.