CLONING AND CHARACTERIZATION OF THE MAJOR OUTER-MEMBRANE PROTEIN GENE(OMPH) OF PASTEURELLA-MULTOCIDA X-73

The major outer membrane protein (OmpH) of Pasteurella multocida X-73 was purified by selective extraction with detergents, followed by size exclusion chromatography. The planar lipid bilayer assay showed that OmpH has pore-forming function. The average single channel conductance in 1.0 M KCI was 0.62 nS. The gene (ompH) encoding OmpH has been isol ated and sequenced by construction of a genomic library and PCR techni ques. The coding region of this gene is 1,059 bp long. The predicted p rimary protein is composed of 353 amino acids, with a 20-amino-acid si gnal peptide. The mature protein is composed of 333 amino acids with a molecular mass of 36.665 kDa. The ompH gene encoding mature protein h as been expressed in Escherichia coli by using a regulatable expressio n system. The ompH gene was distributed among 15 P. multocida serotype s and strain CU. Protection studies showed that OmpH was able to induc e homologous protection in chickens. These findings demonstrate that O mpH is a protective outer membrane porin of strain X-73 and is conserv ed among P. multocida somatic serotypes.