INTERACTION OF PORPHYROMONAS-GINGIVALIS WITH TRANSFERRIN

In this study, we characterized the binding of transferrin to Porphyro monas gingivalis using a classical receptor-binding assay, and examine d the relationship between the binding and availability of transferrin for the growth of P. gingivalis. The binding of I-125-labeled human t ransferrin to P. gingivalis occurred rapidly, reversibly and specifica lly. Scatchard analysis yielded a K-d of 1.37 +/- 0.16 mu M and an app arent number of 1.13 +/- 0.26 x 10(5) receptors per cell. The binding of transferrin was much increased when organisms were grown in iron-li mited conditions. Among the species of black-pigmented anaerobic rods, those strains of P. gingivalis which had high transferrin-binding act ivity exhibited unrestricted growth following the addition of transfer rin to the hemin-free culture medium. On the other hand, the presence of transferrin in the culture medium did not support unrestricted grow th of organisms that had low transferrin-binding activity. These resul ts suggest that the binding of transferrin to P. gingivalis cells may be a preliminary step in iron acquisition, which allows them to surviv e in the healthy periodontal environment.