THE AMINO-TERMINAL DOMAIN OF THE P-PILUS ADHESIN DETERMINES RECEPTOR SPECIFICITY

Pyelonephritic isolates of Escherichia coil commonly express P-pili, w hich mediate bacterial attachment to glycolipids on epithelial cell su rfaces. Three classes of P-pili have been defined, based on varying sp ecificity for galabiose-containing glycolipids. Variation in adhesive capacity is correlated with a shift in preferred host, suggesting that host tropism depends largely on detailed specificity for the globoser ies glycolipids. In this study we examined the importance of the PapG adhesin in determining receptor specificity. Translational fusions wer e constructed between the amino-terminus of the PapG adhesin from each of the three pilus classes and a reporter protein. The binding specif icity of the purified fusion proteins in vitro was identical to that s een with whole bacteria. Adherence of intact bacteria to cultured kidn ey cells was markedly reduced by a monoclonal antibody specific for th e Class III adhesin (previously denoted PrsG), confirming the importan ce of the amino-terminus of PapG in mediating attachment to a receptor when presented on the eukaryotic cell surface. These results suggest that the detailed receptor specificity resides solely within the amino -terminus of the PapG adhesin and is independent of the complex pilus architecture.