Isolation and characterization of the heat-responsive genes in Escherichia coli

The ompC gene expression is induced by increasing temperature as well as osmotic pressure. In this study, a mutant (TD2) defective in this thermoresponse was isolated with transposon Tn10; the mutation was complemented by pMAN55 or pMAN56 containing micF and mapped at 48 min on Escherichia coli K-12. Furthermore, a new gene (hrsA) that suppressed the mutation was cloned. Its nucleotide sequence was analyzed and it was located close to the suc operon at 16.7 min corresponding to #18F11 (Kohara bank) on E. coli genome. In TD2 containing the hrsA on a multicopy plasmid, the ompC expression was induced and dependent on OmpR with increased temperature. The HrsA was found to have Enzyme IIA, IIB, and IIC domains that are homologous to Enzyme II, involved in the fructose-specific PTS (phosphotransferase system). The putative phosphorylation sites (His87 and Cys192) were also conserved in HrsA.