REGULATION AND BINDING-PROPERTIES OF S-FIMBRIAE CLONED FROM ESCHERICHIA-COLI STRAINS CAUSING URINARY-TRACT INFECTION AND MENINGITIS

S fimbriae are able to recognize receptor molecules containing sialic acid and are produced by pathogenic E. coli strains causing urinary tr act infection and menigitis. In order to characterize the correspondin g genetic determinant, termed S fimbrial adhesin (sfa) gene cluster, w e have cloned the S-specific genes from a urinary pathogen and from a meningitis isolate. Nine genes are involved in the production of S fim briae, two of these, sfaB and sfaC code for regulatory proteins being necessary for the expression of S fimbriae. Two promoters, P(B) and P( C), are located in front of these genes. Transcription of the sfa dete rminant is influenced by activation of the promoters via SfaB and SfaC , the action of the H-NS protein and an RNaseE-specific mRNA processin g. In addition, a third promoter, P(A), located in front of the major subunit gene sfaA, can be activated under special circumstances. Four genes of the sfa determinant code for the subunit-specific proteins, S faA (16 kda), SfaG (17 kda), SfaS (14 kda) and SfaH (29 kda). It was d emonstrated that the protein SfaA is the major subunit protein while S faS is identical to the sialic -acid-specific adhesin of S fimbriae. T he introduction of specific mutations into sfaS revealed that a region of six amino acids of the adhesin which includes two lysine and one a rginine residues is involved in the receptor specific interaction of S fimbriae. Additionally, it has been shown that SfaS is necessary for the induction of fimbriation while SfaH plays a role in the stringency of binding of S fimbriae to erythrocytes.