Membrane association and multimerization of secreton component pulC.
The PulC component of the Klebsiella oxytoca pullulanase secretion machinery (the secreton) was found by subcellular fractionation to be associated with both the cytoplasmic (inner) and outer membranes. Association with the outer membrane was independent of other secreton components, including the outer membrane protein PulD (secretin). The association of PulC with the inner membrane is mediated by the signal anchor sequence located close to its N terminus. These results suggest that PulC forms a bridge between the two membranes that is disrupted when bacteria are broken open for fractionation. Neither the signal anchor sequence nor the cytoplasmic N-terminal region that precedes it was found to be required for PulC function, indicating that PulC does not undergo sequence-specific interactions with other cytoplasmic membrane proteins. Cross-linking of whole cells resulted in the formation of a ca. 110-kDa band that reacted with PulC-specific serum and whose detection depended on the presence of PulD. However, antibodies against PulD failed to react with this band, suggesting that it could be a homo-PulC trimer whose formation requires PulD. The data are discussed in terms of the possible role of PulC in energy transduction for exoprotein secretion.
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Unité de Génétique Moléculaire, CNRS URA1773, Institut Pasteur, 75724 Paris Cedex 15, France.
Gérard-Vincent
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Pugsley
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D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000302:isolation & purification* / Q000378:metabolism*; D002458:Cell Fractionation; D002462:Cell Membrane / Q000201:enzymology*; D003001:Cloning, Molecular; D003432:Cross-Linking Reagents; D006026:Glycoside Hydrolases / Q000378:metabolism*; D007709:Klebsiella / Q000201:enzymology* / Q000235:genetics; D008565:Membrane Proteins / Q000302:isolation & purification* / Q000378:metabolism; D009154:Mutation; D011485:Protein Binding; D011487:Protein Conformation; D021382:Protein Sorting Signals
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D003432:Cross-Linking Reagents; D008565:Membrane Proteins; C105759:OutC protein, bacteria; D021382:Protein Sorting Signals; C061378:PulC protein, Klebsiella pneumoniae; C061377:PulD protein, Klebsiella pneumoniae; D006026:Glycoside Hydrolases; C100181:pullulanase