The N-terminal beta-barrel domain of the Escherichia coli K88 periplasmic chaperone FaeE determines fimbrial subunit recognition and dimerization.
The K88 periplasmic chaperone FaeE is a homodimer, whereas the K99 chaperone FanE is a monomer. The structural requirements for dimerization of the K88 fimbrial periplasmic chaperone and for fimbrial subunit-binding specificity were investigated by analysis of mutant chaperones. FaeE contains a C-terminal extension of 19 amino acid residues when compared to FanE and most other fimbrial chaperones. A C-terminal truncate of the K88 chaperone FaeE was constructed that lacked 19 C-terminal amino acid residues. Expression and complementation experiments revealed that this C-terminal shortened chaperone was still functional in binding the K88 major subunit FaeG and K88 biosynthesis. Two hybrid chaperones were constructed. Each hybrid protein contained one beta-barrel domain of FaeE and the other beta-barrel domain of FanE (Fae/FanE or Fan/FaeE, respectively). Expression and complementation experiments revealed that the Fae/FanE but not the Fan/FaeE hybrid chaperone was functional in the formation of K88 fimbriae. The Fan/FaeE hybrid chaperone was active in the bio-synthesis of K99 fimbriae. The truncated FaeE mutant chaperone and the hybrid Fae/FanE chaperone were able to form stable periplasmic protein complexes with the K88 major fimbrial subunit FaeG. Cross-linking experiments suggested that the C-terminal shortened chaperone and the Fae/FanE hybrid chaperone were homodimers, as is the wild-type K88 chaperone. Altogether, the data suggested that the N-terminal beta-barrel domain of a fimbrial chaperone determines subunit specificity. In the case of the K88 periplasmic chaperone, this N-terminal domain also determines dimerization of the protein.
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Department of Molecular Microbiology, BioCentrum Amsterdam, Faculty of Biology, Vrije Universiteit, The Netherlands.
Oudhuis
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Fokkema
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Oudega
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D000595:Amino Acid Sequence; D000942:Antigens, Bacterial / Q000276:immunology; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D001483:Base Sequence; D019281:Dimerization; D000939:Epitopes / Q000276:immunology; D004926:Escherichia coli / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D029968:Escherichia coli Proteins; D010861:Fimbriae, Bacterial / Q000378:metabolism* / Q000648:ultrastructure; D018832:Molecular Chaperones / Q000737:chemistry* / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D017433:Protein Structure, Secondary
D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D000939:Epitopes; D029968:Escherichia coli Proteins; D018832:Molecular Chaperones; C070011:fanE protein, E coli; C070012:faeE protein, E coli