PURIFICATION AND CHARACTERIZATION OF A PUTATIVE FIMBRIAL PROTEIN RECEPTOR OF PORPHYROMONAS-GINGIVALIS/

Porphyromonas gingivalis has been implicated as a major aetiological a gent in certain forms of periodontal disease. P. gingivalis is a Gram- negative, asaccharolytic bacterium that obtains energy from the fermen tation of amino acids derived from the hydrolysis of host protein. Vir ulence factors of this bacterium include the capsule, fimbrial adhesin s, cytotoxins and extracellular hydrolytic enzymes. a 43 kDa fimbrilli n from P. gingivalis has been isolated and characterized. However, the re is evidence that a second type of fimbria exists on the surface of Fl gingivalis. A putative P. gingivalis fimbrial protein from a membra ne preparation has been isolated and identified. This protein was show n to be reactive with sera from patients harbouring P. gingivalis. A 2 8 kDa protein fragment was purified by anion exchange, gel filtration and reversed-phase chromatography. N-terminal sequence analysis of the 28 kDa protein fragment revealed homology to the fimbrial precursor p rotein of Dichelobacter nodosus. A peptide corresponding to the N-term inal 26 amino acyl residues of the 28 kDa protein fragment was synthes ized and used to raise antibodies to the protein. Western blot analysi s after SDS-PAGE of a P. gingivalis membrane preparation using the ant ibodies raised to the synthetic peptide detected three proteins of 36, 41 and 67 kDa. When protease inhibitors were not included in the extr action procedure only the 36 and 41 kDa bands were detected. It would appear, therefore, that the intact protein has an M-r of 67 kDa and th at the 28, 36 and 41 kDa bands represent protein fragments produced by endogenous proteolytic activity. Based on sequence homology, the 67 k Da protein is possibly a sub-unit of a second P. gingivalis fimbrial t ype or a surface receptor.