Subunit 7 or the Qcr7 protein of the cytochrome bc(1) complex in yeast is a nuclear-encoded 14-kDa protein and is essential for formation of a functional bc(1) complex and respiration. It was shown previously that the N-terminal region of the Qcr7 protein might play little role in import but may be essential for correct assembly of the bc(1) complex. To examine the role of the N-terminus in assembly of the bc(1) complex, various N-terminus deletion and point mutants of the QCR7 gene were expressed in yeast strains where the endogenous QCR7 gene has been inactivated. Deletion of the first 8-15 residues after methionine at the N-terminus of the Qcr7 protein was studied and it was shown that except for the Qcr7p-Delta7 mutant, the strains overexpressing deletion mutants (Qcr7p-Delta8 to Qcr7p-Delta14) displayed decreased steady-state levels of iron-sulfur protein (ISP) and 14-kDa (Qcr7) and 11-kDa (Qcr8) subunits, as well as a respiratory defect. It was shown that introducing mutations at the N-terminus of the QCR7 gene in the Delta7 context had more drastic effects on respiration and assembly than in the full-length context, suggesting that the first seven residues at the N-terminus have a role in increasing the stability of the holocomplex. This led to a respiratory-deficient phenotype and drastic decrease in the steady-state levels of Qcr7 (14-kDa) and Qcr8 (11-kDa) proteins. The mutants Qcr7p-Delta7 (R10I), Qcr7p-Delta7 (G12V), Qcr7p-Delta7 (D13G), Qcr7p-Delta7 (D13V), and Qcr7p-Delta7 (D13Y) showed decreases in the steady-state levels of ISP and 14- and 11-kDa subunits, as well as defects in respiration. These results are interpreted in the light of the X-ray crystal structure of the yeast bc(1) complex.CI - Copyright 2001 Academic Press.
|Evidence ID||Analyze ID||Interactor||Interactor Systematic Name||Interactor||Interactor Systematic Name||Type||Assay||Annotation||Action||Modification||Phenotype||Source||Reference||Note|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Gene Ontology Term||Gene Ontology Term ID||Qualifier||Aspect||Method||Evidence||Source||Assigned On||Reference||Annotation Extension|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Phenotype||Experiment Type||Experiment Type Category||Mutant Information||Strain Background||Chemical||Details||Reference|
|Evidence ID||Analyze ID||Regulator||Regulator Systematic Name||Target||Target Systematic Name||Experiment||Conditions||Strain||Source||Reference|