The E. coli signal recognition particle is required for the insertion of a subset of inner membrane proteins.
E. coli homologs of the signal recognition particle (SRP) and its receptor are essential for viability, but their role in protein export is unclear. To elucidate their function, we devised a genome-wide screen to identify genes that encode SRP substrates. Inhibition of the SRP pathway sharply blocked the membrane insertion of several polytopic inner membrane proteins (IMPs) that were predicted to be SRP substrates, but had a smaller effect on the insertion of other IMPs and no significant effect on preprotein translocation. Our results suggest that whereas most E. coli preproteins and some IMPs can utilize SRP-independent targeting pathways effectively, the structural features of a subset of IMPs have required the conservation of an SRP-based targeting machinery.
Ulbrandt
N D
ND
Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
Newitt
J A
JA
Bernstein
H D
HD
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D008565:Membrane Proteins / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D010641:Phenotype; D011498:Protein Precursors / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D018271:Signal Recognition Particle / Q000235:genetics / Q000378:metabolism*; D014169:Transformation, Bacterial
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C082931:Ffh protein, E coli; C087406:FtsY protein, Bacteria; D008565:Membrane Proteins; D011498:Protein Precursors; D018160:Receptors, Cytoplasmic and Nuclear; D011993:Recombinant Fusion Proteins; D018271:Signal Recognition Particle