IDENTIFICATION AND CHARACTERIZATION OF 2 QUIESCENT PORIN GENES, NMPC AND OMPN, IN ESCHERICHIA-COLI-B-E

The genomic DNA of the B-E strain of Escherichia coli has been scrutin ized to detect porin genes that have not been identified so far. South ern blot analysis yielded two DNA segments which proved highly homolog ous to, yet distinct fi om, the ompC, ompF, and phoE porin genes. The two genes were cloned and sequenced. One of them, designated ompN, enc odes a porin which, due to low levels of expression, has eluded prior identification. The functional properties (single-channel conductance) of the OmpN porin, purified to homogeneity, closely resemble those of the OmpC porin from E. coli K-12, The second DNA fragment detected co rresponds to the nmpC gene, which, due to an insertion of an IS1 eleme nt in its coding region, is not expressed in E. roll B-E.