Cloning of the gene encoding the Actinobacillus actinomycetemcomitans serotype b OmpA-like outer membrane protein

The gene encoding an outer membrane protein A (OmpA)-like, heat-modifiable Omp of Actinobacillus actinomycetemcomitans ATCC 43718 (strain Y4, serotype b) was cloned by a PCR cloning procedure. DNA sequence analysis revealed t hat the gene encodes a protein of 346 amino acid residues with a molecular mass of 36.9 kDa. The protein expressed by the cloned gene reacted with a m onoclonal antibody to the previously described 29- kDa Omp (Omp29) of strai n Y4. This monoclonal antibody reacted specifically with Omp29 of A. actino mycetemcomitans (serotype b), but not with any Omp of Escherichia coli, inc luding OmpA. This protein exhibited characteristic heat modifiability on so dium dodecyl sulfate-polyacrylamide gels, showing an apparent molecular mas s of 29 kDa when unheated and a mass of 34 kDa when heated. The N-terminal amino acid sequence of the protein expressed in E. coli perfectly matched t hose deduced from the purified Omp29 of strain Y4, The deduced amino acid s equence of the gene coding for Omp29 from serotype b matched completely (ex cept for valine at position 321) that of a recently reported omp34 gene des cribed for A. actinomycetemcomitans serotype c (NCTC 9710). Because of the conserved nature of the gene within these serotypes, we designated the gene described herein from serotype b as omp34.