Substitution of fifty four homologue (Ffh) in Escherichia coli with the mammalian 54-kDa protein of signal-recognition particle.
The fifty four homologue (Ffh) of Escherichia coli promotes the translocation of a subset of periplasmic, membrane and secreted proteins across the cytoplasmic membrane. The ffh gene product is essential for cell viability and efficient protein export. Here we show that the mammalian homologue signal-recognition particle (SRP) 54 kDa is not able to suppress the translocation defect in an Ffh conditional mutant Wam 113 [Phillips, G.J. & Silhavy, T.J. (1992) Nature 359, 744-746]. The expression of SRP 54kDa, which is increased when Ffh is suppressed in the Wam 113 strain, causes a pleiotropic defect characterised by cell elongation, and increased accumulation of precursor proteins. The accumulation of precursors of outer membrane protein A (Omp A) and maltose-binding protein (MBP), See-B dependent pre-proteins, was less than the Ffh-dependent proteins ribose-binding protein (RBP) and beta-lactamase. Sec B expression was suppressed by Ffh expression. The recombinant SRP 54 kDa, which forms a ribonucleoprotein complex in E coli, was shown to bind to precursor proteins, but is unable to interact with the filamentous temperature-sensitive Y (Fts Y) membrane receptor of the translocation machinery.
Patel
S
S
St. George's Hospital Medical School, London, England.
Austen
B M
BM
D000595:Amino Acid Sequence; D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D002455:Cell Division / Q000235:genetics; D004285:Dogs; D004926:Escherichia coli / Q000166:cytology / Q000235:genetics*; D029968:Escherichia coli Proteins; D005982:Glutathione Transferase / Q000378:metabolism; D006165:Guanylyl Imidodiphosphate / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012261:Ribonucleoproteins / Q000096:biosynthesis; D018271:Signal Recognition Particle / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D014178:Translocation, Genetic
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C082931:Ffh protein, E coli; C087406:FtsY protein, Bacteria; D011498:Protein Precursors; D018160:Receptors, Cytoplasmic and Nuclear; D011994:Recombinant Proteins; D012261:Ribonucleoproteins; C057842:SecB protein, Bacteria; D018271:Signal Recognition Particle; D006165:Guanylyl Imidodiphosphate; D005982:Glutathione Transferase