Adhesins encoded by the gingipain genes of Porphyromonas gingivalis are responsible for co-aggregation with Prevotella intermedia

Abstract

Co-aggregation among bacterial cells caused by the adherence of one bacterial species to another is a potential colonization mechanism. Several putative aggregation factors for co-aggregation betweenPorphyromonas(Por.)gingivalisandPrevotella(Pre.)intermediawere partially purified fromPor. gingivalisvesicles by gel filtration and affinity chromatography. Antisera against the aggregation factors were made. Analysis using these antisera revealed that 18 and 44 kDa proteins might be responsible forPor. gingivalisvesicle-mediated aggregation ofPre. intermedia. Using antiserum against the 18 kDa protein, the DNA region encoding it was cloned fromPor. gingivalisgenomic DNA. Sequence analysis revealed that the DNA region was located within thergpAandkgpgenes, encoding Arg-gingipain (Rgp) and Lys-gingipain (Kgp), respectively, and it encoded non-catalytic adhesin domain regions, namely a C-terminal portion of HGP15, the entire HGP17 sequence and an N-terminal portion of HGP27. A portion of the DNA sequence was also found in the haemagglutinin A (hagA) gene. A recombinant glutathioneS-transferase (GST)–HGP17 fusion protein reacted to antiserum against the 18 kDa protein andPre. intermediacells could adhere to GST–HGP17-conjugated Sepharose 4B beads, indicating that the HGP17 domain protein is responsible forPor. gingivalisvesicle-mediated aggregation ofPre. intermedia.