title: Protein complexes of the Escherichia coli cell envelope.
abstract: Protein complexes are an intrinsic aspect of life in the membrane. Knowing which proteins are assembled in these complexes is therefore essential to understanding protein function(s). Unfortunately, recent high throughput protein interaction studies have failed to deliver any significant information on proteins embedded in the membrane, and many membrane protein complexes remain ill defined. In this study, we have optimized the blue native-PAGE technique for the study of membrane protein complexes in the inner and outer membranes of Escherichia coli. In combination with second dimension SDS-PAGE and mass spectrometry, we have been able to identify 43 distinct protein complexes. In addition to a number of well characterized complexes, we have identified known and orphan proteins in novel oligomeric states. For two orphan proteins, YhcB and YjdB, our findings enable a tentative functional assignment. We propose that YhcB is a hitherto unidentified additional subunit of the cytochrome bd oxidase and that YjdB, which co-localizes with the ZipA protein, is involved in cell division. Our reference two-dimensional blue native-SDS-polyacrylamide gels will facilitate future studies of the assembly and composition of E. coli membrane protein complexes during different growth conditions and in different mutant backgrounds.
authors.affiliation: Department of Biochemistry and Stockholm University, Stockholm SE-106 91, Sweden.
authors.forename: Filippa
authors.initials: F
authors.lastname: Stenberg
authors.forename: Peter
authors.initials: P
authors.lastname: Chovanec
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Maslen
authors.forename: Carol V
authors.initials: CV
authors.lastname: Robinson
authors.forename: Leopold L
authors.initials: LL
authors.lastname: Ilag
authors.forename: Gunnar
authors.initials: G
authors.lastname: von Heijne
authors.forename: Daniel O
authors.initials: DO
authors.lastname: Daley
mesh_terms: D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000494:pharmacology*; D002455:Cell Division; D002462:Cell Membrane / Q000378:metabolism*; D003573:Cytochrome b Group; D003580:Cytochromes / Q000378:metabolism; D019281:Dimerization; D045222:Electron Transport Chain Complex Proteins / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000378:metabolism / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D007477:Ions / Q000737:chemistry; D046911:Macromolecular Substances / Q000737:chemistry; D013058:Mass Spectrometry; D008565:Membrane Proteins / Q000737:chemistry; D009154:Mutation; D010088:Oxidoreductases / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D011485:Protein Binding; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D018797:Cell Cycle Proteins; D003573:Cytochrome b Group; D003580:Cytochromes; D045222:Electron Transport Chain Complex Proteins; D029968:Escherichia coli Proteins; D007477:Ions; D046911:Macromolecular Substances; D008565:Membrane Proteins; C506079:YjdB protein, E coli; D010088:Oxidoreductases; C506078:YhcB protein, E coli; C040077:cytochrome bd terminal oxidase complex, E coli