The OmpC protein of Yersinia enterocolitica: purification and properties

OmpC, one of the major outer membrane proteins of Yersinia enterocolitica, was isolated and purified to homogeneity. When solubilized at room temperature, this protein appeared on SDS polyacrylamide gel electrophoresis as an oligomer. After heating to the temperature of boiling water, the apparent molecular weight of the monomer was 36,000. The incorporation of purified OmpC into black lipid membranes resulted in an increase in membrane conductance demonstrating pore-forming activity. The reconstituted pores exhibited the characteristics of general diffusion pores. They showed cation selectivity and had a single channel conductance of 1.3 nS in 1.0 M KCl. Assuming a constant diameter of the pore, a length of 6 nm (the width of the outer membrane) and the same ion conductivity inside and outside the pore, the diameter of the pore protein was estimated as 1.0 nm. Polyclonal antibodies were raised against the native, pore-forming protein preparation. These antibodies did not recognize the denatured form of the protein, but cross-reacted with native OmpC and OmpF of Escherichia coli. The regulation of OmpC expression in Y. enterocolitica was dependent on the osmolarity of the medium in the same way as in E. coli.