THE CLONING, EXPRESSION AND SEQUENCE-ANALYSIS OF A 2ND PORPHYROMONAS-GINGIVALIS GENE THAT CODES FOR A PROTEIN INVOLVED IN HEMAGGLUTINATION

It has been suggested that Porphyromonas gingivalis may possess more t han one hemagglutinin. We have previously reported the cloning of a ge ne (hagA) that encodes a hemagglutinin. In this study we report the cl oning, characterization, and sequencing of a second gene (hagB) that e ncodes a protein that also appears to be involved in hemagglutination. Antiserum to the clone (ST 7) was found to inhibit hemagglutination b y P. gingivalis 381, and hemagglutinating inhibition activity of anti- P. gingivalis antiserum was reduced by adsorption of the antiserum wit h cells of clone ST 7. Restriction mapping and Southern analysis indic ates there is little or no DNA homology between this cloned 4.8-kb Hin dIII DNA fragment and a cloned hemagglutinin gene we have previously d escribed. Minicell analysis of the cloned P. gingivalis chromosomal DN A fragment revealed that the major gene product is a 49-kDa protein. I mmunoaffinity chromotography using purified rabbit immunoglobulin G ag ainst the cloned protein resulted in the purification of a major react ive 49- to 50-kDa protein from a P. gingivalis cell lysate. Nucleotide sequence analysis revealed the hagB open reading frame to be 1053 nuc leotides in length with a mol% G+C of 59.9% coding for a protein of 35 0 residues with a calculated molecular weight of 39.375 kDa. This prot ein was also determined to be basic and hydrophilic and to contain a p otential signal peptide. Comparison of both the nucleotide and derived amino acid sequences with computer-based databases did not reveal any significant homologies between hagB and any other previously sequence d genes.