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S. cerevisiae coq5 null mutants require over‐expression of Coq8 kinase for rescue by E. coli COQ5 homolog ubiE
Author(s) -
Nguyen Theresa P.T.,
Clarke Catherine F.
Publication year - 2013
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.27.1_supplement.585.16
Subject(s) - mutant , complementation , saccharomyces cerevisiae , protein subunit , yeast , biology , gene , biochemistry , genetics
Coenzyme Q (Ubiquinone or Q) is an essential lipid electron carrier in the respiratory electron chain. In Saccharomyces cerevisiae, eleven genes ( COQ1–9, ARH1, YAH1 ) are required for coenzyme Q biosynthesis, several of which encode proteins involved in a multi‐subunit complex. One of these genes, COQ5 , encodes a C ‐methyltransferase responsible for making the late stage intermediate demethoxy Q 6 (DMQ 6 ). COQ5 has three conserved methyltransferase motifs, and yeast point mutants within or adjacent to these motifs ( coq5–2 , coq5–5 ) lack Coq5 activity but retain steady state levels of the Coq5 polypeptide. We show that ubiE , the E. coli homolog for COQ5 , is able to rescue coq5–2 and coq5–5 point mutants, but is unable able to rescue the yeast coq5 Δ null mutant. However when putative kinase Coq8 is over‐expressed, ubiE is able to rescue the yeast COQ5 knockout. We demonstrate that co‐expression of COQ8 and ubiE in a coq5 Δ null mutant restores Q 6 levels and supports growth on non‐fermentable carbon sources. We also show the effects of complementation on the Coq multi‐subunit complex in the coq5 mutants via 2D Blue native‐PAGE. By observing the accumulation of Q intermediates in coq5 mutants, we have been able to elucidate steps within a novel Q biosynthetic pathway. Studies supported by National Science Foundation Grant 0919609.