INHIBITION OF COAGGREGATION BETWEEN PORPHYROMONAS-GINGIVALIS AND STREPTOCOCCUS-ORALIS BY FIBRINOGEN FRAGMENTS

The localization of regions of fibrinogen that inhibit coaggregation b etween Porphyromonas gingivalis and Streptococcus oralis was investiga ted. The coaggregation was inhibited by A alpha and gamma chains, but not by B beta chain. The inhibitory activity of fragment D was more po tent than that of fragment E. Some cyanogen bromide-treated fragments isolated from A alpha and gamma chains including the NH2-terminal 148- 207 amino acid residues of A alpha chain (A alpha 148-207) and gamma 1 -78 showed inhibitory activities. A alpha 148-207 was further digested with lysyl endopeptidase. A alpha 158-176 and A alpha 192-206 which c ontained four and two arginine residues, respectively, retained the in hibitory activities. When the arginine residues of these two peptides were modified by phenylglyoxal, the inhibitory activities were much re duced. These findings suggest that the arginine residues of some speci fic regions of fibrinogen may play an important role in the inhibition of the coaggregation.