Ir. Henderson et al., Characterization of pic, a secreted protease of Shigella flexneri and enteroaggregative Escherichia coli, INFEC IMMUN, 67(11), 1999, pp. 5587-5596
We have identified and characterized a secreted protein, designated Pie, wh
ich is encoded on the chromosomes of enteroaggregative Escherichia coli (EA
EC) 042 and Shigella flexneri 2457T. The product of the pic gene is synthes
ized as a 146.5-kDa precursor molecule which is processed at the N and C te
rmini during secretion, allowing the release of a mature protein (109.8 kDa
) into the culture supernatant. The deduced amino acid sequence of Pic show
s high homology to autotransporter proteins, particularly a subgroup termed
the SPATEs (serine protease autotransporters of the Enterobacteriaceae). P
resent in all members of this subgroup is a motif similar to the active sit
es of certain serine proteases. Pic catalyzes gelatin degradation, which ca
n be abolished by disruption of the predicted proteolytic active site. Func
tional analysis of the Pic protein implicates this factor in mucinase activ
ity, serum resistance, and hemagglutination. Our data suggest that Pic may
be a multifunctional protein involved in enteric pathogenesis.