Nucleotide and deduced protein sequence of the extracellular, serine basic protease gene (bprB) from Dichelobacter nodosus strain 305: comparison with the basic protease gene (bprV) from virulent strain 198

Abstract

In earlier studies, it appeared that benign strains of the Gram-negative, obligate anaerobe, Dichelobacter nodosus, were devoid of the extracellular, serine basic protease (pI approximately 9.5) of virulent strains. However, Southern and PCR analysis have shown a homologous gene (bprB) in the representative benign strain 305. The deduced amino acid sequence of the prepro- and mature protease regions of bprB confirmed this homology and showed 97% sequence identity with the bprV precursor from virulent strain 198. Identity in the carboxy-terminal extension region was 90%. Expression studies in Escherichia coli transformed with bprB, showed that the gene was capable of the production of an active protease. A protease, albeit with a lower iso-electric point (approximately 8.6), was isolated from D. nodosus culture supernatants and shown to cross-react with antibodies raised against the more basic protease from strain 198. The amino acid sequence encoded by the strain 305 gene revealed two additional acidic residues consistent with a lowered iso-electric point and supported the conclusion that bprB and bprV produce equivalent basic proteases.