ABSTRACT
Pili are protein polymers composed of approximately a thousand copies of a major pilus subunit and several minor pilus subunits that play important roles in adhesion presentation, polymerization initiation, and termination. Pili are an effective means that pathogenic bacteria have developed to present adhesins to eukaryotic cell receptors. P pili specifically recognize a terminal or internal Gala(1-4)Gal moiety in epithelial cell surface glycolipids via the papG product. Variations in the N-terminal amino acid sequences of the G adhesins are correlated with slight differences in receptor specificity. Chaperone-target recognition can best be investigated in a system where both the chaperone structure and the target proteins are known. The P-pilus biogenesis system fills these criteria and, therefore, was used as a model system to study chaperone-target interactions. Slonim et al. determined that pilus subunits bound in the cleft of PapD and that the binding relied on Arg8 and Lysl 12, which are invariant cleft residues in the periplasmic chaperone family.
