The complete primary structure of pilin from Haemophilus influenzae type b strain Eagan

Adherence ofHaemophilus influenzae type b (Hib) to human oropharyngeal cells is mediated by pili which are proteinaceous filaments that extend outward from the bacterial cell surface. Pili from Hib strain Eagan were purified, and the primary structure of the major subunit, pilin, was determined. Sequencing of overlapping peptides showed the mature protein to be comprised of 196 amino acids and to have an Mr of 21,152. The amino terminal sequence was found to be homologous with the sequence previously reported for Hib strain M43 and also to have significant homology to pilins of other gram-negative pathogenic bacteria. Furthermore, Hib pilin had two cysteinyl residues in the amino terminal portion of the protein which were separated by 40 residues (positions 21 and 61); a motif found in other bacterial pilins. The data show that Hib pilin has structural features common to other bacterial pilins.