Abstract
Analysis of amino acid sequences reported for the major outer membrane proteins of E. coli, including the porins (OmpF, OmpC and PhoE), the phage .lambda. receptor (LamB) and another protein (OmpA), revealed several regions of local homology that is statistically significant. The implications of this observation are discussed in relation to the evolutionary origins of these proteins, and to the mechanism of export of these proteins to the outer membrane.