Biogenesis of F71 and F72 fimbriae of uropathogenic Escherichia coli: influence of the FsoF and FstFG proteins and localization of the Fso/FstE protein.

The F71 and F71 P-fimbriae of Escherichia coli are encoded by the fso (F seven one) and fst (F seven two) gene clusters, respectively (Van Die et al., 1984; 1985). With the immunocytochemical gold-labelling technique it was demonstrated that both the FsoE and FstE proteins are non-adhesive minor fimbrial sub-units located at the tip of the fimbrial structure. The FsoF and FstFG proteins play an important role in the initiation of polymerization of the minor and major subunits into the fimbrial structure.

Cloning of Klebsiella pneumoniae pqq genes and PQQ biosynthesis in Escherichia coli.

We have cloned genes from Klebsiella pneumoniae which are required for pyrroloquinoline quinone (PQQ) biosynthesis. The cloned 6.7 kb fragment can complement several chromosomal pqq mutants. Escherichia coli strains are unable to synthesize PQQ but E. coli strains containing the cloned 6.7 kb K. pneumoniae fragment can synthesize PQQ in large amounts and E. coli pts mutants can be complemented on minimal glucose medium by this clone.

Biogenesis of F7(1) and F7(2) fimbriae of uropathogenic Escherichia coli: influence of the FsoF and FstFG proteins and localization of the Fso/FstE protein.

The F7(1) and F7(2) P-fimbriae of Escherichia coli are encoded by the fso (F seven one) and fst (F seven two) gene clusters, respectively (Van Die et al., 1984; 1985). With the immunocytochemical gold-labelling technique it was demonstrated that both the FsoE and FstE proteins are non-adhesive minor fimbrial subunits located at the tip of the fimbrial structure. The FsoF and FstFG proteins play an important role in the initiation of polymerization of the minor and major subunits into the fimbrial structure.

Functional analysis of the fsoC gene product of the F7(1) (fso) fimbrial gene cluster.

Contrary to what would be expected from data in the literature, mutations in the fsoC gene of the F7(1) (fso) P-fimbrial gene cluster do not completely block fimbrial biogenesis. fsoC mutants still express small amounts of fimbriae of normal length, which carry the non-adhesive minor subunit protein, FsoE, but lack the adhesin, FsoG. The FsoC protein operates at the same stage in fimbrial biogenesis as the FsoF and FsoG proteins. The data suggest that FsoC, FsoF and FsoG interact to form an initiation complex for fimbrial biogenesis.

Immunocytochemical analysis of P-fimbrial structure: localization of minor subunits and the influence of the minor subunit FsoE on the biogenesis of the adhesin.

Antibodies recognizing the non-adhesive minor P-fimbral subunit protein E and the P-fimbrial adhesin were used in an immunocytochemical analysis of P-fimbrial structure. It was demonstrated that P-fimbriae of the serotypes F71, F72 and F11 carry their adhesin in a complex with protein E. These complexes are commonly found at the tip of the fimbrial structure. In P-fimbriae of serotype F9, expressed by the uropathogenic Escherichia coli strain 21086, adhesin-protein E complexes are localized at the tips as well as along the shafts of the fimbriae. Protein E of F71 fimbriae (FsoE) plays a catalysing role in the biogenesis of the adhesin, but has no effect on the eventual localization of the adhesin.

Nucleotide sequence and structure of the Klebsiella pneumoniae pqq operon.

A 6940 bp Klebsiella pneumoniae chromosomal DNA fragment, containing genes involved in pyrroloquinoline quinone (PQQ) biosynthesis, was sequenced. Six open reading frames, pqqA, pqqB, pqqC, pqqD, pqqE and pqqF were identified in the pqq operon, which coded for polypeptides of 2764 (23 amino acids), 33,464, 28,986, 10,436, 42,881 and 83,616 Da, respectively. The transcription startpoint was mapped by primer extension analysis, upstream of pqqA, and promoter boxes could be identified. The gene products of pqqB, pqqC, pqqE and pqqF were detected in maxi-cells and the molecular weights of the proteins corresponded with the molecular weights deduced from the nucleotide sequence. The gene products of pqqA, pqqB, pqqC, pqqD and pqqE show 49%-64% identity in amino acid sequence with those of pqqIV, pqqV, pqqI, pqqII and pqqIII respectively in the cloned pqq cluster of Acinetobacter calcoaceticus. The 84 kDa protein encoded by pqqF, which is not present in the cloned pqq cluster of A. calcoaceticus but which is essential for PQQ biosynthesis in K. pneumoniae and Escherichia coli, seems to belong to a family of proteases.

Overproduction and high-yield purification of phospholipase A from the outer membrane of Escherichia coli K-12.

The cloned gene for the outer-membrane-bound phospholipase A from Escherichia coli was placed under control of the strong PL promoter of phage lambda. Induction of PL resulted in a 250-fold overexpression up to about 2% total cellular protein. This overproduced enzyme was indistinguishable from the wild-type enzyme. A homogeneous phospholiphase A preparation was obtained in high yield from overproducing bacteria, using the zwitterionic detergent C12-Sulfobetaine and anion-exchange chromatography. Detergent gradients were found to exert great influence on the elution characteristics. Considerations for the choice of optimal detergent gradients are discussed. The purified enzyme migrated as a single 29-kDa band in SDS/polyacrylamide gels, and required Ca(II) for activity. Maximum activity was displayed by enzyme samples taken from solutions with detergent concentrations near the critical micelle concentration. However, upon switching from high to optimal detergent concentration, maximum activity was restored in several hours, probably reflecting a slow conformational transition of the protein. Because the final pure protein was found to hydrolyze phospholipids in the intact erythrocyte membrane, a densely packed bilayer, we assume that this protein is in its biological native state.

The pro- and mature forms of the E. coli K-12 outer membrane phospholipase A are identical.

The nucleotide sequence of the pldA gene, coding for the outer membrane (OM) phospholipase A of Escherichia coli K-12, and flanking sequences, was determined. Data were obtained from sequences of overlapping deletions which had been generated in vitro from both ends of the gene, using DNase I in the presence of Mn2+ and Bal31 nuclease. The deduced amino acid sequence of the pldA gene product is the first primary sequence of a membrane-bound phospholipase. The complete PldA protein contains 260 amino acids, which include a putative signal sequence, and has a calculated mol. wt. of 29 946 similar to that of the purified protein. Furthermore we found the N terminus of the purified protein to be blocked and the overall amino acid composition to be consistent with the one deduced from the complete pldA gene. Analysis of proteins synthesized in minicells with a pldA coding plasmid in the presence of 8% ethanol did not reveal any new bands on polyacrylamide gels, whereas the control beta-lactamase clearly showed its unprocessed form under the same conditions. These data are consistent with the empirical prediction from the primary sequence, that the PldA protein lacks any signal peptidase 'target' site. We therefore conclude that the PldA protein is exported to the OM without proteolytic removal of the signal peptide.

Multifunctional nature of P fimbriae of uropathogenic Escherichia coli: mutations in fsoE and fsoF influence fimbrial binding to renal tubuli and immobilized fibronectin.

P fimbriae of the F7(1) serotype of Escherichia coli are composed of a major subunit, FsoA, and of three minor proteins named FsoG, FsoE, and FsoF. FsoG is the Gal alpha(1-4)Gal-specific lectin. We assessed mutated recombinant strains each deficient in one fimbrial component for adhesion to frozen sections of rat cortical kidney and to fibronectin immobilized on glass. Rat kidney lacks the Gal alpha(1-4)Gal-containing glycolipids. The fsoG mutant strain was as adhesive to sections of rat kidney and to fibronectin-coated glass as was the recombinant strain expressing the complete fso gene cluster. The fsoA mutant strain was highly adhesive to fibronectin and to kidney sections. In the rat kidney, the adhesion of these strains was predominantly localized to sites of basolateral membranes of tubuli. The fsoE and the fsoF mutant strains were slightly less adhesive to kidney structures and failed to adhere to fibronectin. The fsoE, fsoF double mutant strain adhered neither to fibronectin nor to kidney sections. None of the fso recombinant strains reacted with soluble fibronectin, suggesting that the interaction is dependent on the conformation of the fibronectin molecules. Recombinant strains expressing the F7(2), F8, F11, F13, and F14 serovariants of the P fimbria also showed adherence to immobilized fibronectin. The results show that in addition to binding to globoseries of glycolipids via the G protein, the P fimbriae of uropathogenic E. coli exhibit a tissue-binding property influenced by fsoE and fsoF gene products and with affinity for basolateral membranes and fibronectin.

Genetic manipulation of major P-fimbrial subunits and consequences for formation of fimbriae.

The influence of genetic manipulation of the structural genes coding for major P-fimbrial subunits on the formation of fimbriae in Escherichia coli was studied. Deletion of two regions that code for hypervariable parts of the P fimbrillin resulted in strong reduction or total absence of fimbria production. Replacement of deleted amino acids by other amino acid residues restored the formation of fimbriae. The hypervariable regions may be important for biogenesis of fimbriae by imposing correct spacing between conserved regions of the protein. The potential for substituting amino acids in the P-fimbrial subunit opens interesting possibilities for use of fimbriae as carriers of foreign antigenic determinants. An antigenic determinant of foot-and-mouth disease virus (FMDV) was incorporated in the F11 fimbrial subunit. Hybrid fimbriae, recognized by an FMDV-specific neutralizing monoclonal antibody directed against FMDV, were formed.

F1C fimbriae of a uropathogenic Escherichia coli strain: genetic and functional organization of the foc gene cluster and identification of minor subunits.

The genetic organization of the foc gene cluster has been studied; six genes involved in the biogenesis of F1C fimbriae were identified. focA encodes the major fimbrial subunit, focC encodes a product that is indispensable for fimbria formation, focG and focH encode minor fimbrial subunits, and focI encodes a protein which shows similarities to the subunit protein FocA. Apart from the FocA major subunits, purified F1C fimbriae contain at least two minor subunits, FocG and FocH. Minor proteins of similar size were observed in purified S fimbriae. Remarkably, some mutations in the foc gene cluster result in an altered fimbrial morphology, i.e., rigid stubs or long, curly fimbriae.