Molecular interactions of Porphyromonas gingivalis fimbriae with host proteins: Kinetic analyses based on surface plasmon resonance

Fimbriae of Porphyromonas gingivalis are thought to play an important role in the colonization and invasion of periodontal tissues. In this study, we analyzed the interactions of P. gingivalis fimbriae,vith human hemoglobin, fibrinogen, and salivary components (i.e., proline-rich protein [PRP], prol ine-rich glycoprotein [PRC], and statherin) based on surface plasmon resona nce (SPR) spectroscopy with a biomolecular interaction analyzing system (BI Acore), The real-time observation showed that the fimbriae interacted more quickly with hemoglobin and PRG than with other proteins and more intensely with fibrinogen. The significant association constant (k(a)) values obtain ed by BIAcore demonstrated that the interactions between fimbriae and these host proteins are specific. These estimated K-a values were not too differ ent; however, the K-a values for hemoglobin (2.43 x 10(6)) and fibrinogen ( 2.16 x 10(6)) were statistically greater than those for the salivary protei ns (1.48 x 10(6) to 1.63 x 10(6)), The K-a value of anti-fimbriae immunoglo bulin G for fimbriae was estimated to be 1.22 x 10(7), which was 6.55-fold higher than the mean K-a value of the host proteins, Peptide PRP-C, a poten t inhibitor of PRP-fimbriae interaction, dramatically inhibited fimbrial as sociation to PRP and PRG and was also inhibitory against other host protein s by BIAcore. The binding of fimbriae to these proteins was also evaluated by other methods with hydroxyapatite beads or polystyrene microtiter plates . The estimated binding abilities differed considerably, depending on the a ssay method that was used. It was noted that the binding capacity of PRP wa s strongly diminished by immobilization on a polystyrene surface. Taken tog ether, these findings suggest that P. gingivalis fimbriae possess a strong ability to interact with the host proteins which promote bacterial adherenc e to the oral cavity and that SPR spectroscopy is a useful method for analy zing specific protein-fimbriae interactions.