Required for type IV pilus biogenesis and competence. Could function as a pore for exit of the pilus but also as a channel for entry of heme and antimicrobial agents and uptake of transforming DNA. Homododecamer. Tetramer of trimer (By similarity). Associated to the membrane through its C-terminus. Cells show decreased piliation and transformation efficiency. It uses hemoglobin as a heme and iron source in the absence of a hemoglobin receptor and it has elevated sensitivities to various antimicrobial compounds. Belongs to the bacterial secretin family. PilQ subfamily.