title: SecG is an auxiliary component of the protein export apparatus of Escherichia coli.
abstract: SecY, SecE and SecG form the membrane-embedded core complex of the Escherichia coli protein export apparatus. These three proteins co-purify and can be co-immunoprecipitated, demonstrating that they are closely associated. While SecE and SecY are generally accepted as essential components of translocase, the role of SecG is more ambiguous. It is commonly believed that deletion of secG causes a cold-sensitive phenotype and a severe defect in export, even though some reports have indicated otherwise. However, we demonstrate that deletion of secG does not produce a cold-sensitive phenotype or a strong export defect in most genetic backgrounds. The more common result is that deletion of secG causes only a mild export defect and does not result in conditional lethality. We propose that the role of SecG is not fundamental to the export process, but is merely auxiliary--as suggested previously by biochemical data--and is physiologically important only when cells are otherwise compromised.
authors.affiliation: Department of Microbiology and Immunology, University of North Dakota School of Medicine and Health Sciences, Grand Forks 58202-9037, USA. aflower@medicine.nodak.edu
authors.forename: A M
authors.initials: AM
authors.lastname: Flower
authors.forename: L L
authors.initials: LL
authors.lastname: Hines
authors.forename: P L
authors.initials: PL
authors.lastname: Pfennig
mesh_terms: D000483:Alleles; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001693:Biological Transport, Active / Q000235:genetics; D003080:Cold Temperature; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029968:Escherichia coli Proteins; D017353:Gene Deletion; D005798:Genes, Bacterial; D007613:Kanamycin Resistance / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010641:Phenotype; D000069816:SEC Translocation Channels
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D000069816:SEC Translocation Channels; C088616:SecG protein, E coli