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. Author manuscript; available in PMC: 2015 Aug 1.
Published in final edited form as: Microbiol Spectr. 2015 Jan 29;3(3):MDNA3-0015-2014. doi: 10.1128/microbiolspec.MDNA3-0015-2014

Figure 1. Type IV Pilus and DNA Uptake.

Figure 1

A. Type IV Pilus – The Tfp is a several micron long, 60 angstrom wide fiber anchored in the inner membrane by PilG that extends through the PilQ secretin pore. Composed mainly of the major pilin PilE (pilin), which is processed by a dedicated protease, PilD. The PilF and PilT NTPases mediate extension and retraction of the pilus through polymerization and depolymerization of the pilin subunits. B. Competence Pseudopilus – Hypothesized pseudopilus that could mediate transformation. Utilizes the type IV pilus complex including the PilQ pore but is not an extended fiber. Possible localization of ComP to the pseudopilus could mediate specific DNA binding. C. DNA Uptake Model - Retraction of the (pseudo)pilus mediated by PilT brings the initial length of DNA into the periplasm. DNA is then bound by a protein or protein complex possibly containing ComE which mediates import of the remaining length of DNA into the periplasm. The inner membrane protein ComA facilitates DNA entry into the cytoplasm.