Targeting of porin to the outer membrane of Escherichia coli. Rate of trimer assembly and identification of a dimer intermediate.
Porin, a transmembrane protein in the outer membrane of Escherichia coli, exists in a trimeric structure which is not dissociated during sodium dodecyl sulfate-polyacrylamide gel electrophoresis at 25 degrees C. This unusual stability was utilized in the study of the conformational changes which accompany the targeting of porin to the outer membrane. A delay of 16-44 s between completion of synthesis of a monomer and its assembly into a trimer was found from the ratio of monomers to trimers found in exponentially growing cells. Pulse-chase experiments showed that rapid processing of precursor OmpF molecules was followed by assembly into sodium dodecyl sulfate-resistant oligomers with a half-time of 20 s at 30 degrees C. An intermediate in assembly was isolated by immunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis below 10 degrees C and was identified as a metastable dimer.
Reid
J
J
Department of Microbiology and Immunology, University of California, Berkeley 94720.
Fung
H
H
Gehring
K
K
Klebba
P E
PE
Nikaido
H
H
D001425:Bacterial Outer Membrane Proteins / Q000032:analysis* / Q000096:biosynthesis; D002462:Cell Membrane / Q000648:ultrastructure*; D004926:Escherichia coli / Q000648:ultrastructure*; D007700:Kinetics; D008970:Molecular Weight; D011108:Polymers / Q000032:analysis; D018272:Porins; D011498:Protein Precursors / Q000378:metabolism
D001425:Bacterial Outer Membrane Proteins; D011108:Polymers; D018272:Porins; D011498:Protein Precursors