Probing conserved surfaces on PapD.
PapD is the periplasmic chaperone required for the assembly of P pili in pyelonephritic strains of Escherichia coli. It consists of two immunoglobulin-like domains bisected by a subunit binding cleft. PapD is the prototype member of a super family of immunoglobulin-like chaperones that work in concert with their respective ushers to assemble a plethora of adhesive organelles including pilus- and non-pilus-associated adhesins. Three highly conserved residue clusters have been shown to play critical roles in the structure and function of PapD, as determined by site-directed mutagenesis. The in vivo stability of the chaperone depended on the formation of a buried salt bridge within the cleft. Residues along the G1 beta strand were required for efficient binding of subunits consistent with the crystal structure of PapD-peptide complexes. Finally, Thr-53, a residue that is part of a conserved band of residues located on the amino-terminal domain surface opposite the subunit binding cleft, was also found to be critical for pilus assembly, but mutations at Thr-53 did not interfere with chaperone-subunit complex formation.
Department of Molecular Microbiology, Washington University School of Medicine, St Louis, MO 63110, USA.
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Hung
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Knight
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Hultgren
D018830:Adhesins, Escherichia coli / Q000737:chemistry; D001426:Bacterial Proteins / Q000737:chemistry* / Q000502:physiology*; D002847:Chromatography, Agarose; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000737:chemistry*; D029968:Escherichia coli Proteins; D036781:Fimbriae Proteins; D010861:Fimbriae, Bacterial / Q000737:chemistry / Q000502:physiology; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000737:chemistry* / Q000502:physiology*; D016297:Mutagenesis, Site-Directed; D033903:Periplasmic Proteins; D011233:Precipitin Tests; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013997:Time Factors
D018830:Adhesins, Escherichia coli; C078802:AtpA protein, E coli; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D018832:Molecular Chaperones; C084330:PapD protein, E coli; C092426:PapG protein, E coli; D033903:Periplasmic Proteins; D036781:Fimbriae Proteins