CHARACTERIZATION OF OUTER-MEMBRANE PROTEINS OF XENORHABDUS-NEMATOPHILUS

The major outer membrane proteins of the primary and secondary phase v ariants of Xenorhabdus nematophilus produced during exponential and st ationary phase growth were characterized. OpnP, the most highly expres sed outer membrane protein of X. nematophilus, was purified as a monom er with a molecular weight of 30,000. The amino acid composition of Op nP was very similar to that of the porin proteins, OmpF and OmpC, of E scherichia coli, N-terminal amino acid sequence analysis revealed that residues 1-27 of the mature OpnP shared 60% sequence identity with Om pF. In vitro pore function analysis of purified OpnP indicated that th e single channel conductance values were similar to that measured for OmpF. These results suggest that OpnP is the OmpF-like porin protein i n X. nematophilus. Three additional proteins, OpnA, OpnB and OpnS were induced during stationary phase growth. We show that the stationary p hase proteins, OpnA and OpnB, were not produced in secondary phase cel ls. OpnB was present at a high level in stationary phase cells grown a t 19-30 degrees C, and was repressed in cells grown at 34 degrees C. O pnA was optimally produced at 30 degrees C and was not present in cell s grown at lower and higher temperatures. The production of OpnS was n ot dependent on growth temperature. In contrast, another outer membran e protein, OpnT, was strongly induced as the growth temperature was el evated from 19 degrees to 34 degrees C.