Fig. 8: Schematic showing positioning of RcpA-TadD complex within the outer membrane and relative to other TadSS components.

The RcpA N-domain is an Alphafold model and its orientation is modelled based on the X. citri VirB9 N-terminal domain periplasmic ring⁴⁴. Hidden Markov model analysis of Flp1 revealed close homology with PilA-N from the Geobacter sulfurreducens type 4 pilus filament⁷⁹ (as well as archaeal flagellin). The Flp pilus shown therefore represents the ~5 Å diameter helical filament formed by PilA-N subunit from PDB 7TGG. RcpB which is predicted to locate within the outer membrane has been omitted for clarity as has the prepilin peptidase TadV. The MinD-like TadZ was generated from PDB code 3FKQ. RcpC has been shown to localise to both inner and outer membrane fractions¹⁹.