QSR1, an essential yeast gene with a genetic relationship to a subunit of the mitochondrial cytochrome bc1 complex, codes for a 60 S ribosomal subunit protein.
QSR1 (quinol-cytochrome c reductase subunit-requiring) is a highly conserved, essential gene in Saccharomyces cerevisiae that was identified through a synthetic lethal screen by its genetic relationship to QCR6, the gene for subunit 6 (Qcr6p) of the mitochondrial cytochrome bc1 complex. The function of the QSR1-encoded protein (Qsr1p) and its relationship to the QCR6-encoded protein are unknown. When yeast cell lysates are fractionated by density gradient centrifugation, Qsr1p separates from organelles and sediments with a uniformly sized population of particles that are similar to eukaryotic ribosomes upon velocity gradient centrifugation. When 40 S and 60 S ribosomal subunits are separated on velocity gradients, Qsr1p is found exclusively with the 60 S subunits, where it is a stoichiometric component. Extracts prepared from qsr1-1 cells are defective in in vitro translation assays relative to the wild type. In yeast cell lysates in which QCR6 rescues an otherwise lethal qsr1-1 mutation, Qcr6p is found only in mitochondria, both in respiratory-competent cells and in rho0 cells in which the bc1 complex is no longer present. These results suggest that suppression of the qsr1-1 mutation by QCR6 occurs by a trans-relationship across the outer mitochondrial membrane.
Dick
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Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
Karamanou
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Trumpower
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D014450:Electron Transport Complex III / Q000235:genetics*; D005656:Fungal Proteins / Q000235:genetics*; D005800:Genes, Fungal; D008928:Mitochondria / Q000235:genetics; D012269:Ribosomal Proteins / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins
D005656:Fungal Proteins; C093333:RPL10 protein, S cerevisiae; D012269:Ribosomal Proteins; D029701:Saccharomyces cerevisiae Proteins; D014450:Electron Transport Complex III