The oral spirochete Treponema denticola is a keystone periodontal pathogen that, in association with members of a complex polymicrobial oral biofilm, contributes to tissue damage and
alveolar bone loss in
periodontal disease. Virulence-associated behaviors attributed to T. denticola include disruption of the host cell extracellular matrix, tissue penetration and disruption of host cell membranes accompanied by dysregulation of host immunoregulatory factors. T. denticola
dentilisin is associated with several of these behaviors.
Dentilisin is an outer membrane-associated complex of acylated
subtilisin-family PrtP
protease and two other
lipoproteins, PrcB and PrcA, that are unique to oral spirochetes.
Dentilisin is encoded in a single operon consisting of prcB-prcA-prtP. We employ multiple approaches to study mechanisms of
dentilisin assembly and PrtP
protease activity. To determine the role of each
protein in the
protease complex, we have made targeted mutations throughout the
protease locus, including polar and nonpolar mutations in each gene (prcB, prcA, prtP) and deletions of specific PrtP domains, including single base mutagenesis of key PrtP residues. These will facilitate distinguishing between host cell responses to
dentilisin protease activity and its acyl groups. The boundaries of the divergent promoter region and the relationship between
dentilisin and the adjacent
iron transport operon are being resolved by incremental deletions in the sequence immediately 5' to the
protease locus. Comparison of the predicted three-dimensional structure of PrtP to that of other
subtilisin-like
proteases shows a unique PrtP C-terminal domain of approximately 250 residues. A survey of global gene expression in the presence or absence of
protease gene expression reveals potential links between
dentilisin and
iron uptake and homeostasis in T. denticola. Understanding the mechanisms of
dentilisin transport, assembly and activity of this unique
protease complex may lead to more effective prophylactic or therapeutic treatments for
periodontal disease.