Binding of a histidine‐rich peptide to Porphyromonas gingivalis

: Prophyromonas gingivalis 381 cells were incubated with 125I‐histidine‐rich polypeptide (histatin) 5 in the presence or absence of unlabeled histatin 5, to evaluate the histatin‐binding capacity of the cells. The binding of histatin 5 was rapid, reversible, saturable and specific. The number of histatin 5‐binding sites per cell was 3 600, and the dissociation constant (Kd) was in the order of 10−6 M. These findings suggest that histatin interacts with certain bacterial cells through specific binding sites on their surface, and will allow the development of a histatin radioreceptor assay.