In vitro multimerization and membrane insertion of bacterial outer membrane secretin PulD.
Synthesis of the Klebsiella oxytoca outer membrane secretin PulD, or its membrane-associated core domain, in a liposome-supplemented Escherichia coli in vitro transcription-translation system resulted in the formation of multimers that appeared as typical dodecameric secretin rings when examined by negative-stain electron microscopy. Cryo-electron microscopy of unstained liposomes and differential extraction by urea indicated that the secretin particles were inserted into the liposome membranes. When made in the presence of the detergent Brij-35, PulD and the core domain were synthesized as monomers. Both proteins caused almost immediate growth cessation when synthesized in E. coli without a signal peptide. The small amounts of PulD synthesized before cell death appeared as multimers with characteristics similar to those of the normal outer membrane secretin dodecamers. It was concluded that multimerization and membrane insertion are intrinsic properties of secretin PulD that are independent of a specific membrane environment or membrane-associated factors. The closely related Erwinia chrysanthemi secretin OutD behaved similarly to PulD in all assays, but the more distantly related Neisseria meningitidis secretin PilQ did not form multimers either when made in vitro in the presence of liposomes or when made in E. coli without its signal peptide. This is the first report of the apparently spontaneous in vitro assembly and membrane insertion of a large outer membrane protein complex. Spontaneous multimerization and insertion appear to be restricted to outer membrane proteins closely related to PulD.
Guilvout
Ingrid
I
Molecular Genetics Unit and CNRS URA2172, Institut Pasteur, 25, rue du Dr. Roux, 75724 Paris, France.
Chami
Mohamed
M
Berrier
Catherine
C
Ghazi
Alexandre
A
Engel
Andreas
A
Pugsley
Anthony P
AP
Bayan
Nicolas
N
D001425:Bacterial Outer Membrane Proteins / Q000096:biosynthesis / Q000378:metabolism* / Q000648:ultrastructure; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D020285:Cryoelectron Microscopy; D036781:Fimbriae Proteins / Q000378:metabolism; D041121:Klebsiella oxytoca / Q000166:cytology / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D050356:Lipid Metabolism / Q000187:drug effects; D050505:Mutant Proteins / Q000302:isolation & purification / Q000378:metabolism; D021382:Protein Sorting Signals; D020836:Protein Structure, Quaternary; D014508:Urea / Q000494:pharmacology
D001425:Bacterial Outer Membrane Proteins; D050505:Mutant Proteins; D021382:Protein Sorting Signals; C084295:pilQ protein, bacteria; D036781:Fimbriae Proteins; D014508:Urea