Báo cáo khoa học: Complementation of coenzyme Q-deficient yeast by coenzyme Q analogues requires the

Complementation of coenzyme Q-deficient yeast by

coenzyme Q analogues requires the isoprenoid side chain

Andrew M. James1

, Helena M. Cocheme´

1,2, Masatoshi Murai3

, Hideto Miyoshi3

and Michael P. Murphy1

1 Medical Research Council Mitochondrial Biology Unit, Wellcome Trust ⁄ MRC Building, Cambridge, UK

2 Institute of Healthy Ageing and GEE, University College London, Darwin Building, London, UK

3 Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto, Japan

Introduction

CoenzymeQ (CoQ) is composed of a head group that

cycles between reduced ubiquinol and oxidized ubiqui￾none forms and a hydrophobic isoprenoid tail that

keeps the redox activity of the head group located

within the lipid bilayer. The length of the isoprenoid tail

varies between species, with Saccharomyces cerevisiae,

rats and humans predominantly synthesizing forms of

CoQ containing six (CoQ6), nine (CoQ9) and 10

(CoQ10) isoprenoid units, respectively. CoQ is synthe￾sized endogenously by a series of enzymes localized to

Keywords

coenzyme Q; diauxic shift; mitochondria;

ubiquinone; yeast

Correspondence

A. M. James, Medical Research Council

Mitochondrial Biology Unit, Wellcome

Trust ⁄ MRC Building, Hills Road, Cambridge

CB2 0XY, UK

Fax: +44 1223 252905

Tel: +44 1223 252903

E-mail: aj@mrc-mbu.cam.ac.uk

Website: http://www.mrc-mbu.cam.ac.uk

(Received 18 December 2009, revised

2 February 2010, accepted 22 February

2010)

doi:10.1111/j.1742-4658.2010.07622.x

The ubiquinone coenzyme Q (CoQ) is synthesized in mitochondria with a

large, hydrophobic isoprenoid side chain. It functions in mitochondrial res￾piration as well as protecting membranes from oxidative damage. Yeast

that cannot synthesize CoQ (DCoQ) are viable, but cannot grow on nonfer￾mentable carbon sources, unless supplied with ubiquinone. Previously we

demonstrated that the isoprenoid side chain of the exogenous ubiquinone

was important for growth of a DCoQ strain on the nonfermentable sub￾strate glycerol [James AM et al. (2005) J Biol Chem 280, 21295–21312]. In

the present study we investigated the structural requirements of exoge￾nously supplied CoQ2 for growth on glycerol and found that the first dou￾ble bond of the initial isoprenoid unit is essential for utilization of

respiratory substrates. As CoQ2 analogues that did not complement growth

on glycerol supported respiration in isolated mitochondria, discrimination

does not occur via the respiratory chain complexes. The endogenous form

of CoQ in yeast (CoQ6) is extremely hydrophobic and transported to mito￾chondria via the endocytic pathway when supplied exogenously. We found

that CoQ2 does not require this pathway when supplied exogenously and

the pathway is unlikely to be responsible for the structural discrimination

observed. Interestingly, decylQ, an analogue unable to support growth on

glycerol, is not toxic, but antagonizes growth of DCoQ yeast in the pres￾ence of exogenous CoQ2. Using a DCoQ double-knockout library we iden￾tified a number of genes that decrease the ability of yeast to grow on

exogenous CoQ. Here we suggest that CoQ or its redox state may be a sig￾nal for growth during the shift to respiration.

Abbreviations

CoQ, coenzyme Q with an isoprenoid side chain; CoQ1–10, coenzyme Q with a side chain of one to 10 isoprenoid units; DCoQ, yeast strains

lacking the ability to synthesize endogenous CoQ6; FCCP, carbonylcyanide-p-trifluoromethoxy-phenylhydrazone; I, fluorescence after the

addition of ubiquinone; I0, initial fluorescence; Isc1, inositol sphingolipid phospholipase C; PP2A, protein phosphatase 2A; Pyr16, 1-pyrene

hexadecanoic acid; YPD, yeast extract, peptone, glucose; YPG, yeast extract, peptone, glycerol; YPGG, yeast extract, peptone, glycerol with

glucose.

FEBS Journal 277 (2010) 2067–2082 ª 2010 The Authors Journal compilation ª 2010 FEBS 2067