Characterization of coaggregation and fibrinogen-binding by Porphyromonas gingivalis

We have examined whether the adhesin of Porphyromonas gingivalis which aggregates Streptococcus oralis contributes to its fibrinogen-binding. Various properties of coaggregation between P. gingivalis and S. oralis were compared with those of fibrinogen-binding to P. gingivalis cells. The coaggregation activity was measured by a turbidimetric method and the fibrinogen-binding activity was determined by using 125I-fibrinogen. Both the activities showed maximum values in the pH range from 5.0 to 6.0 and they were inhibited by arginine and lysine. Heating treatment of P. gingivalis 381 cells at 75 degrees C abrogated the activities. However, treatment of P. gingivalis 381 cells with proteinase K considerably reduced the fibrinogen-binding activity but not the coaggregation activity. Metal ions such as Zn2+ and Cu2+ inhibited the coaggregation activity but enhanced the fibrinogen-binding activity. The results also indicated that P. gingivalis strains 381, ATCC 33277 and SU-3 showed relatively higher activities both in coaggregation and fibrinogen-binding, whereas P. gingivalis strains W83, 51 and 165 showing lower fibrinogen-binding activity than P. gingivalis 381 did not coaggregate with S. oralis ATCC 9811. These findings suggest that coadhesin of P. gingivalis with S. oralis is not be associated with its fibrinogen-binding.