title: Genetic screen yields mutations in genes encoding all known components of the Escherichia coli signal recognition particle pathway.
abstract: We describe the further utilization of a genetic screen that identifies mutations defective in the assembly of proteins into the Escherichia coli cytoplasmic membrane. The screen yielded mutations in each of the known genes encoding components of the E. coli signal recognition particle pathway: ffh, ffs, and ftsY, which encode Ffh, 4.5S RNA, and FtsY, respectively. In addition, the screen yielded mutations in secM, which is involved in regulating levels of the SecA component of the bacterium's protein export pathway. We used a sensitive assay involving biotinylation to show that all of the mutations caused defects in the membrane insertions of three topologically distinct membrane proteins, AcrB, MalF, and FtsQ. Among the mutations that resulted in membrane protein insertion defects, only the secM mutations also showed defects in the translocation of proteins into the E. coli periplasm. Genetic evidence suggests that the S382T alteration of Ffh affects the interaction between Ffh and 4.5S RNA.
authors.affiliation: Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: Hongping
authors.initials: H
authors.lastname: Tian
authors.forename: Jon
authors.initials: J
authors.lastname: Beckwith
mesh_terms: D018528:ATP-Binding Cassette Transporters; D000251:Adenosine Triphosphatases / Q000235:genetics; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000235:genetics; D005798:Genes, Bacterial; D058619:Maltose-Binding Proteins; D008565:Membrane Proteins / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics; D009004:Monosaccharide Transport Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009154:Mutation; D019897:Periplasm / Q000378:metabolism; D021381:Protein Transport; D012329:RNA, Bacterial; D012335:RNA, Ribosomal / Q000235:genetics; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D000069816:SEC Translocation Channels; D000081416:SecA Proteins; D012641:Selection, Genetic; D018271:Signal Recognition Particle / Q000235:genetics*
chemical_list: D018528:ATP-Binding Cassette Transporters; D000251:Adenosine Triphosphatases; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D058619:Maltose-Binding Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D009004:Monosaccharide Transport Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D012329:RNA, Bacterial; D012335:RNA, Ribosomal; D018160:Receptors, Cytoplasmic and Nuclear; D011993:Recombinant Fusion Proteins; D000069816:SEC Translocation Channels; D000081416:SecA Proteins; D018271:Signal Recognition Particle; C409968:4.5S RNA; C083496:AcrB protein, E coli; C082931:Ffh protein, E coli; C068023:FtsQ protein, E coli; C087406:FtsY protein, Bacteria; C461599:maltose transport system, E coli