Adapter that links the PapG adhesin to the distal end of the tip fibrillum. PapF is required for the correct presentation of the adhesin at the distal end of the tip fibrillum. Pili are polar filaments radiating from the surface of the bacterium to a length of 0.5-1.5 micrometers and numbering 100-300 per cell, and enable bacteria to colonize the epithelium of specific host organs. At the tip of the pili. Strains of E.coli that cause infection of the human urinary tract produce pap-pili which are hair-like appendages consisting of about 1000 helically arranged subunits of the protein PapA. These pili mediate binding to digalactoside-containing glycolipids present on the epithelial cells which line the urinary tract.