title: SecY variants that interfere with Escherichia coli protein export in the presence of normal secY.
abstract: As an approach for studying how SecY, an integral membrane protein translocation factor of Escherichia coli, interacts with other protein molecules, we isolated a dominant negative mutation, secY-d1, of the gene carried on a plasmid. The mutant plasmid severely inhibited export of maltose-binding protein and less severely of OmpA, when introduced into sec+ cells. It inhibited growth of secY and secE mutant cells, but not of secA and secD mutant cells or wild-type cells. The mutation deletes three amino acids that should be located at the interface of cytoplasmic domain 5 and transmembrane segment 9. We also found that some SecY-PhoA fusion proteins that lacked carboxy-terminal portions of SecY but retain a region from periplasmic domain 3 to transmembrane segment 7 were inhibitory to protein export. We suggest that these SecY variants are severely defective in catalytic function of SecY, which requires cytoplasmic domain 5 and its carboxy-terminal side, but retain the ability to associate with other molecules of the protein export machinery, which requires the central portion of SecY; they probably exert the 'dominant negative' effects by competing with normal SecY for the formation of active Sec complex. These observations should provide a basis for further genetic analysis of the Sec protein complex in the membrane.
authors.affiliation: Department of Cell Biology, Kyoto University, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Shimoike
authors.forename: Y
authors.initials: Y
authors.lastname: Akiyama
authors.forename: T
authors.initials: T
authors.lastname: Baba
authors.forename: T
authors.initials: T
authors.lastname: Taura
authors.forename: K
authors.initials: K
authors.lastname: Ito
mesh_terms: D000469:Alkaline Phosphatase / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport / Q000235:genetics; D002455:Cell Division; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D005799:Genes, Dominant; D009154:Mutation; D010957:Plasmids; D011993:Recombinant Fusion Proteins / Q000235:genetics; D000069816:SEC Translocation Channels
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D011993:Recombinant Fusion Proteins; D000069816:SEC Translocation Channels; C057841:SecY protein, E coli; D000469:Alkaline Phosphatase