DISRUPTION OF ESCHERICHIA-COLI HEPA, AN RNA POLYMERASE-ASSOCIATED PROTEIN, CAUSES UV SENSITIVITY

During the development of purification procedures for Escherichia coil RNA polymerase (RNAP), we noticed the consistent co-purification of a 110-kDa polypeptide. Here, we report the identification of the 110-kD a protein as the product of the hepA gene, a member of the SNF2 family of putative helicases. We have cloned the hepA gene and overexpressed and purified the HepA protein. We show in vitro that RNAP preparation s have an ATPase activity only in the presence of HepA and that HepA b inds core RNAP competitively with the promoter specificity sigma(70) s ubunit with a 1:1 stoichiometry and a dissociation constant (K-d) Of 7 5 nM. An E. coli strain with a disruption in the hepA gene shows sensi tivity to ultraviolet light.