Subunit IV of cytochrome bc1 complex from Rhodobacter sphaeroides. Localization of regions essential for interaction with the three-subunit core complex.

Journal Article (Journal Article)

Recombinant subunit IV mutants which identify the regions essential for restoration of bc(1) activity to the three-subunit core complex of Rhodobacter sphaeroides were generated and characterized. Four C-terminal truncated mutants: IV(1-109), IV(1-85), IV(1-76), and IV(1-40) had 100, 0, 0, and 0% of reconstitutive activity of the wild-type IV, indicating that residues 86-109 are essential. IV(1-109) is associated with the core complex in the same manner as the wild-type IV while mutants IV(1-85), IV(1-76), and IV(1-40) do not associate with the core complex, indicating that subunit IV requires its transmembrane helix region (residues 86-109) for assembly into the bc(1) complex. Since GST-IV(86-109) fusion protein has little reconstitutive activity, some region(s) in residues 1-85 are required for bc(1) activity restoration after subunit IV is incorporated into the complex through the transmembrane helix, presumably by interaction with cytochrome b in the core complex. The interacting regions are identified as residues 41-53 and 77-85, since mutants IV(21-109), IV(41-109), IV(54-109), and IV(77-109) had 95, 98, 53, and 53% of the reconstitutive activity of the wild-type IV. These two interacting regions are on the cytoplasmic side of the chromatophore membrane and closed to the DE loop and helix G of cytochrome b, respectively.

Full Text

Duke Authors

Cited Authors

  • Tso, SC; Shenoy, SK; Quinn, BN; Yu, L

Published Date

  • May 19, 2000

Published In

Volume / Issue

  • 275 / 20

Start / End Page

  • 15287 - 15294

PubMed ID

  • 10748084

International Standard Serial Number (ISSN)

  • 0021-9258

Digital Object Identifier (DOI)

  • 10.1074/jbc.M907367199


  • eng

Conference Location

  • United States