The XcpV/GspI Pseudopilin Has a Central Role in the Assembly of a Quaternary Complex within the T2SS Pseudopilus - Douzi, B; Durand, E; Bernard, C; Alphonse, S; Cambillau, C; Filloux, A; Tegoni, M; Voulhoux, R (JOURNAL OF BIOLOGICAL CHEMISTRY, 2009)