PIL4_ECOLX Propilin is the precursor of the pilus subunit, pilin, that forms conjugative pili, the filamentous surface appendages required for cell-to-cell contact during the earlier stages of bacterial conjugation, and that retract after contact is established. Mature pilin is assembled with the help of traQ and traX (By similarity). traA Pilin 120 MNTVLSVQGASAPVKKKSFFSKFTRLNMLRLARAVIPAAVLMMFFPQLAMAAQGQDLMASGNTTVKATFGKDSSVVKWVVLAEVLVGAVMYMMTKNVKFLAGFAIISVFIAVGMAVVGLK