Subunit IV of Cytochrome bc 1 Complex from Rhodobacter sphaeroides
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(1â109), IV(1â85), IV(1â76), and IV(1â40) had 100, 0, 0, an...
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Veröffentlicht in: | The Journal of biological chemistry 2000-05, Vol.275 (20), p.15287-15294 |
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Hauptverfasser: | , , , |
Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | 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(1â109), IV(1â85), IV(1â76), and IV(1â40) had 100,
0, 0, and 0% of reconstitutive activity of the wild-type IV, indicating that residues 86â109 are essential. IV(1â109) is associated
with the core complex in the same manner as the wild-type IV while mutants IV(1â85), IV(1â76), and IV(1â40) do not associate
with the core complex, indicating that subunit IV requires its transmembrane helix region (residues 86â109) for assembly into
the bc
1 complex. Since GST-IV(86â109) fusion protein has little reconstitutive activity, some region(s) in residues 1â85 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 41â53 and 77â85, since mutants IV(21â109), IV(41â109),
IV(54â109), and IV(77â109) 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. |
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ISSN: | 0021-9258 1083-351X |
DOI: | 10.1074/jbc.M907367199 |