Structural determinants of Actinomyces sortase SrtC2 required for membrane localization and assembly of type 2 fimbriae for interbacterial coaggregation and oral biofilm formation.

As a pioneer colonizer of the oral cavity, Actinomyces oris expresses proteinaceous pili (also called fimbriae) to mediate the following two key events in biofilm formation: adherence to saliva deposits on enamel and interbacterial associations. Assembly of type 2 fimbriae that directly facilitate coaggregation with oral streptococci and Actinomyces biofilm development requires the class C sortase SrtC2. Although the general sortase-associated mechanisms have been elucidated, several structural attributes unique to the class C sortases require functional investigation.