Characterization of receptor-mediated signal transduction by Escherichia coli type IIa heat-labile enterotoxin in the polarized human intestinal cellline T84

The eib genes of Escherichia coli encode surface-exposed proteins which bin d immunoglobulins (Ig) such as the Fc fragment of human IgG (IgG Fc) in a n onimmune manner. The Eib proteins belong to a family which includes YadA of Yersinia, UspA2 of Moraxella, and DsrA of Haemophilus ducreyi. This family of surface-exposed proteins shares several features, such as the ability t o impart resistance to human serum complement and a tendency to exist as st able multimers. Four genes, eibA, eibC, eibD and eibE, were previously iden tified and cloned from ECOR-9, a strain from the E. coli reference collecti on. EibC, -D, and -E bind human serum IgA in addition to IgG, but no IgA bi nding has been observed for EibA. Here, we report the cloning of a new eib gene, eibF, from a second strain of E. coli, ECOR-2. The product, EibF, has a relatively strong preference for IgA. Like the other eib genes, eibF att enuates serum sensitivity, occurs as a stable multimer, and is associated w ith a prophage. By subcloning portions of the eibA and eibF genes, we have identified distinct sequence segments sufficient to cause Ig binding, multi merization, and discrimination between IgA and IgG. The ability to multimer ize is associated with a sequence close to the C terminus that is homologou s to other family members such as YadA. Binding of IgG Fe is associated wit h a sequence that is highly conserved among all Eib proteins but otherwise unique. Binding of IgA is associated with a sequence of EibF that is not si milar to any EibA sequence.