Molecular aspects of biogenesis of Escherichia coli Dr Fimbriae: characterization of DraB-DraE complexes.
The Dr hemagglutinin of uropathogenic Escherichia coli is a fimbrial homopolymer of DraE subunits encoded by the dra operon. The dra operon includes the draB and draC genes, whose products exhibit homology to chaperone-usher proteins involved in the biogenesis of surface-located polymeric structures. DraB is one of the periplasmic proteins belonging to the superfamily of PapD-like chaperones. It possesses two conserved cysteine residues characteristic of the FGL subfamily of Caf1M-like chaperones. In this study we obtained evidence that DraB cysteines form a disulfide bond in a mature chaperone and have the crucial function of forming the DraB-DraE binary complex. Expression experiments showed that the DraB protein is indispensable in the folding of the DraE subunit to a form capable of polymerization. Accumulation of DraB-DraE(n) oligomers, composed of head-to-tail subunits and the chaperone DraB, was observed in the periplasm of a recombinant E. coli strain which expressed DraB and DraE (but not DraC). To investigate the donor strand exchange mechanism during the formation of DraE oligomers, we constructed a series of DraE N-terminal deletion mutants. Deletion of the first three N-terminal residues of a potential donor strand resulted in a DraE protein lacking an oligomerization function. In vitro data showed that the DraE disulfide bond was not needed to form a binary complex with the DraB chaperone but was essential in the polymerization process. Our data suggest that assembly of Dr fimbriae requires a chaperone-usher pathway and the donor strand exchange mechanism.
Piatek
Rafal
R
Department of Microbiology, Gdańsk University of Technology, ul. Narutowicza 11/12, 80-952 Gdańsk, Poland.
Zalewska
Beata
B
Kolaj
Olga
O
Ferens
Michal
M
Nowicki
Bogdan
B
Kur
Józef
J
D018829:Adhesins, Bacterial / Q000737:chemistry / Q000502:physiology*; D000595:Amino Acid Sequence; D004220:Disulfides; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000502:physiology*; D010861:Fimbriae, Bacterial / Q000502:physiology*; D018832:Molecular Chaperones / Q000737:chemistry / Q000502:physiology*; D008969:Molecular Sequence Data; D033903:Periplasmic Proteins / Q000737:chemistry / Q000502:physiology*; D021122:Protein Subunits
D018829:Adhesins, Bacterial; D004220:Disulfides; C465563:DraE protein, E coli; D029968:Escherichia coli Proteins; D018832:Molecular Chaperones; C084330:PapD protein, E coli; D033903:Periplasmic Proteins; D021122:Protein Subunits