Porphyromonas gingivalis is a keystone pathogen associated with chronic periodontitis. This is a progressive inflammatory disease of the tooth’s supporting tissues which results in the destruction of those tissues and ultimately leading to tooth loss. Its major virulence factors include three cysteine proteinases named gingipains (RgpA, RgpB and Kgp) that are secreted via the Type IX Secretion System (T9SS). These, together with approximately 30 other proteins, are secreted to the cell surface and anchored to the outer membrane by covalent modification to an anionic lipopolysaccharide (A-LPS) via the novel Gram negative sortase, PorU. PorU is localised on the cell surface where it cleaves the conserved C-terminal domain signal (CTD) of T9SS substrates and conjugates their new C-termini to A-LPS using a transpeptidase-like mechanism. This study aimed to determine how newly secreted substrates are delivered to the PorU sortase. Outer membrane vesicles were analysed by two dimensional blue-native PAGE (2D BN-PAGE). A 440 kDa-attachment complex was identified in the wild-type (WT) strain comprising of PorU:PorV:PorQ:PorZ. In mutant strains, sub-complexes comprising of PorU:PorV or PorQ:PorZ were identified at smaller native sizes suggesting that PorU and PorZ are anchored to the cell surface via interaction with the PorV and PorQ β–barrel outer membrane proteins, respectively. Analysis of porU mutants and a CTD cleavage mutant substrate revealed accumulation of immature T9SS substrates in a PorV-bound form. Quantitative label-free proteomics of WT whole cell lysates estimated that the proportion of secretion channels:attachment complexes:free PorV:T9SS substrates was 1:6:110:2000 supporting a role for PorV as a shuttle protein to deliver the secreted proteins to the attachment complex on the cell surface for signal cleavage and A-LPS modification.