1. Genetics of E. coli fimbriae.
Genetics of E. coli fimbriae. Genes required for the expression of functional pili are characteristically linked in gene clusters. The genetic organization of these clusters is illustrated for ETEC fimbriae CS1, CFA/I, CS3, and CS6, and for members of the Dr family, found in DAEC and EAEC. Italicized terms in parentheses represent the gene designations, to be followed by the specific letter under the corresponding arrow to the right. Arrows of similar fill pattern have genetic and functional homology; black arrows represent structural subunits. The known functions of the genes in the Dr cluster are listed below the corresponding genes. These functions can be extrapolated to arrows of similar fill pattern in the CS3 and CS6 gene cluster. The usher and chaperone genes from the Dr, CS6, and CS3 clusters have homology to the genes serving these functions inpap fimbriae: usher proteins are OMPs which serve as pores for the transport and assembly of the fimbrial shaft; fimbrial chaperones bind to the fimbrial subunit proteins in the periplasmic space and prevent premature folding and degradation. CS1 and CFA/I accessory genes, required for assembly and transport of the fimbriae, are homologous to each other but not to CS3, CS6, or the Dr family. CS6 has an unusual organization in that the first two genes of the cluster apparently encode heterologous major subunit proteins (699); the significance of this feature is not yet understood.
James P. Nataro, and James B. Kaper Clin. Microbiol. Rev. 1998; doi: /CMR