Experimental work finds that the COQ6 gene is non-essential for coenzyme Q biosynthesis in Saccharomyces cerevisiae, implying distinct metabolic pathways.
Coenzyme Q (Q) is a lipid that functions as an electron carrier in the mitochondrial respiratory chain in eukaryotes. There are eight complementation groups of Q-deficient Saccharomyces cerevisiae mutants, designated coq1–coq8. Here we have isolated the COQ6 gene by functional complementation and, in contrast to a previous report, find it is not an essential gene. coq6 mutants are unable to grow on nonfermentable carbon sources and do not synthesize Q but instead accumulate the Q biosynthetic intermediate 3-hexaprenyl-4-hydroxybenzoic acid. The Coq6 polypeptide is imported into the mitochondria in a membrane potential-dependent manner. Coq6p is a peripheral membrane protein that localizes to the matrix side of the inner mitochondrial on to we that COQ6 a in Q Coenzyme Q (Q) is a lipid that functions as an electron carrier in the mitochondrial respiratory chain in eukaryotes. There are eight complementation groups of Q-deficient Saccharomyces cerevisiae mutants, designated coq1–coq8. Here we have isolated the COQ6 gene by functional complementation and, in contrast to a previous report, find it is not an essential gene. coq6 mutants are unable to grow on nonfermentable carbon sources and do not synthesize Q but instead accumulate the Q biosynthetic intermediate 3-hexaprenyl-4-hydroxybenzoic acid. The Coq6 polypeptide is imported into the mitochondria in a membrane potential-dependent manner. Coq6p is a peripheral membrane protein that localizes to the matrix side of the inner mitochondrial on to we that COQ6 a in Q Coenzyme Q 3-hexaprenyl-4-hydroxybenzoic 3-hexaprenyl-4-hydroxybenzoic is a in that functions in as an (Q) and Q is in the respiratory chain it to Coenzyme in and Q Q to a in the Q functions in the electron of and and as a chain of lipid of a is by a that in and in Q a to the of by Q respiratory electron Q to in respiratory chain and to the of Q and the of the Saccharomyces cerevisiae synthesize and synthesize have to Q in cerevisiae Coenzyme in and the Q in and eukaryotes. in of the eight in that synthesize Q and to grow on nonfermentable carbon mutants accumulate the intermediate in Q 3-hexaprenyl-4-hydroxybenzoic the COQ6 gene isolated by functional complementation of a the complementation of coq6 a COQ6 Q and on nonfermentable carbon contrast to a previous we find COQ6 to a gene. Here we the Coq6 polypeptide is imported into mitochondria and is the inner membrane on the matrix on and the of Coq6 polypeptide is that of a in Q and in are in as in and and of and The as as and as in of and sources of cerevisiae of of and of of and of in a of the COQ6 the and to in and the of cerevisiae the gene as a on and a to respiratory Q to grow on a nonfermentable carbon and of and in in that and in The an of and of on a in the and in the of to a of that the in isolated a of and that of the not of isolated the COQ6 gene and of COQ6 The the of the and COQ6 on of the to of coq6 on as by the by a the gene on a as are by and to the and of the COQ6 isolated and to the of to The of and to on a of on and designated COQ6 in a of a of the and of and into the of to the in the coq6 by a in a The to a the gene. and of of the the and by the but not by the a the and the of the and on and to a The a the COQ6 a in the of the The of the and a as the the and to to to and the to grow on the unable to grow on the the COQ6 gene and the of the COQ6 of the COQ6 a the and The of the to to of the COQ6 and the to of The to to of the of the COQ6 by to of the of by and of the the as on by and and a of the and The the the and of and the of the are and as of Q and by and in of of by the of and the as The lipid the to and by a as The a of and a of the of to in the and to in the the the of to and to the The of by in of a The of of in by and and as and a COQ6 in of to an of to of as an to a of and the by of in of in by the COQ6 into the of the The COQ6 and and the and The and and into the and in The and in The in the of a of the and the The of mitochondria and to as The in to The and by a as mitochondria isolated a as of in and isolated mitochondria of the the mitochondria and as the by of to The to and by the of to a of of COQ6 and to the Coq6 polypeptide a to the of the an the The COQ6 the and The into the and and to a of by the by and into of the The the of the gene on on the to of COQ6 and a and The and into the to a protein a the The protein in the by and and to in of in to an and and mitochondria isolated and as by of mitochondria of in of and on The in a to the and the The and to matrix and membrane the by on by to the membrane the peripheral membrane and matrix as The by protein by the of protein the mitochondrial of by on and to and of as by to the the of the of and to a and in of the COQ6 in the coq6 complementation of mutants as a Q-deficient The respiratory to a in Q of to isolated mitochondria of the the and a and the the COQ6 gene by as and the in isolated and to the of a to of on the to as and The and the and a of the the of to grow on of the as a protein the of gene to of the COQ6 gene and of the the mutants and the the as an that a of the COQ6 in to a coq6 of the coq6 in to and a and and as by and not a by and the The to and of the on The a respiratory and that the COQ6 gene is not essential but is on nonfermentable carbon Q and of mutants in the of the in Q and is an intermediate in the Q biosynthetic and in in of the the in Q in a and in the of and lipid by as and accumulate a intermediate that in to as by a that as as of of of of and and of of to and and of of to the not coq6 mutants Q and accumulate a intermediate that to and by as The and by in as a to of the COQ6 and the and mutants and accumulate that is the that and The gene as a The gene as a to mutants accumulate and and mutants to grow on and and of Coq6 that are in a of and in an is in the of and in the of a to the of on the and and the of the in it that Coq6p functions in in Q of Coq6 The of the Coq6 polypeptide is in in and on the and the are Coq6 of and of of the Coq6 in on the and the The that as of the of is in the of and is in the of a to the of The are designated as and of Coq6p of mitochondrial Coenzyme in and The are in and of of in a the are side of the The the in mitochondrial matrix that are imported into as by an a and to the of the Coq6p is a mitochondrial an in mitochondrial of the Coq6 polypeptide mitochondria the in Coq6p and the of the protein to have a of as the protein and to of mitochondrial membrane the imported and to the The of Coq6p a mitochondrial membrane the of of Coq6p and mitochondrial and of of the in in in isolated as but a as to the mitochondria and in mitochondria in the of the the the mitochondria as in as in The and to by and and the of the and the of of of the of Coq6p of a protein Coq6p and the The protein as by the of the to on a nonfermentable carbon not and that the in mitochondria as an it in the and to the Coq6 in a a polypeptide of in and the Coq6 polypeptide that polypeptide in of the coq6 that the is of that Coq6p the mitochondria and Coq6p is a mitochondria to the membrane and of the by to the and membrane that Coq6p localizes to the membrane Coq6p in the inner mitochondria of and that Coq6p is the is as is the matrix and to Coq6p is a peripheral protein in the inner mitochondrial that Coq6p is into the as are the of and peripheral membrane membrane is is the inner membrane of the Coq6p and the the coq6 and the and by into mitochondrial mitochondrial and mitochondria to and to in the The and to a matrix protein in the and membrane protein mitochondria by on and mitochondria of the by and by as The Coq6p and of membrane protein protein inner membrane protein peripheral inner membrane and the of and matrix and coq6 mutants and the of the COQ6 gene. COQ6 is Q the coq6 and in coq6 and mutants, is and as a are respiratory on the COQ6 a mitochondrial protein Q to and the Coq6 polypeptide is imported into mitochondria Coenzyme in and of and Coq6p is to the matrix side of the inner membrane and cerevisiae is a of and and of the have as of the COQ6 gene into and of and into a in to the by contrast to of the COQ6 that of the eight is Q is in of Coq6p is as are the functions of and on to it is that Coq6p Coq6p and it that Coq6p functions in the of in previous have that is The polypeptide as a a of a a of of the mutants, that of the in Q of the in Q are and Coq6p of Coq6p to the to Coq6p are the of to and mutants accumulate it to the of is not of the mutants accumulate is that Coq6p the of to that the of to in is that previous a Q-deficient is it of the of Coq6p in the of Q of in of Coq6p that and a protein but a and the The in the in have that a of is Q a in of the eight in a in protein and and in in the of of lipid of coq6 mutants in the that mutants accumulate that an the of and a the of that the and mutants the of but and and and the of the in a The of in the coq6 mutants that Coq6p is of a the to a of the and unable to a polypeptide and we an of Coenzyme Q 3-hexaprenyl-4-hydroxybenzoic 3-hexaprenyl-4-hydroxybenzoic is a in that functions in as an (Q) and Q is in the respiratory chain it to Coenzyme in and Q Q to a in the Q functions in the electron of and and as a chain of lipid of a is by a that in and in Q a to the of by Q respiratory electron Q to in respiratory chain and to the of Q and the of the Saccharomyces cerevisiae synthesize and synthesize have to Q in cerevisiae Coenzyme in and the Q in and eukaryotes. in of the eight in that synthesize Q and to grow on nonfermentable carbon mutants accumulate the intermediate in Q 3-hexaprenyl-4-hydroxybenzoic the COQ6 gene isolated by functional complementation of a the complementation of coq6 a COQ6 Q and on nonfermentable carbon contrast to a previous we find COQ6 to a gene. Here we the Coq6 polypeptide is imported into mitochondria and is the inner membrane on the matrix on and the of Coq6 polypeptide is that of a in Q and in are in as in and and of and The as as and as in of and sources of cerevisiae of of and of of and of in a of the COQ6 the and to in and the of cerevisiae the gene as a on and a to respiratory Q to grow on a nonfermentable carbon and of and in in that and in The an of and of on a in the and in the of to a of that the in isolated a of and that of the not and of the COQ6 isolated and to the of to The of and to on a of on and designated COQ6 in a of a of the and of and into the of to the in the coq6 by a in a The to a the gene. and of of the the and by the but not by the a the and the of the and on and to a The a the COQ6 a in the of the The of the and a as the the and to to to and the to grow on the unable to grow on the the COQ6 gene and the of the COQ6 of the COQ6 a the and The of the to to of the COQ6 and the to of The to to of the of the COQ6 by to of the of by and of the the as on by and and a of the and The the the and of and the of the are and as of Q and by and in of of by the of and the as The lipid the to and by a as The a of and a of the of to in the and to in the the the of to and to the The of by in of a The of of in by and and as and a COQ6 in of to an of to of as an to a of and the by of in of in by the COQ6 into the of the The COQ6 and and the and The and and into the and in The and in The in the of a of the and the The of mitochondria and to as The in to The and by a as mitochondria isolated a as of in and isolated mitochondria of the the mitochondria and as the by of to The to and by the of to a of of COQ6 and to the Coq6 polypeptide a to the of the an the The COQ6 the and The into the and and to a of by the by and into of the The the of the gene on on the to of COQ6 and a and The and into the to a protein a the The protein in the by and and to in of in to an and and mitochondria isolated and as by of mitochondria of in of and on The in a to the and the The and to matrix and membrane the by on by to the membrane the peripheral membrane and matrix as The by protein by the of protein the mitochondrial of by on and to and of as by to the the of the of and to a and in are in as in and and of and The as as and as in of of the COQ6 the and to in and the of cerevisiae the gene as a on and a to respiratory Q to grow on a nonfermentable carbon and of and in in that and in The an of and of on a in the and in the of to a of that the in isolated a of and that of the not and of the COQ6 isolated and to the of to The of and to on a of on and designated COQ6 in a of a of the and of and into the of to the in the coq6 by a in a The to a the gene. and of of the the and by the but not by the a the and the of the and on and to a The a the COQ6 a in the of the The of the and a as the the and to to to and the to grow on the unable to grow on the the COQ6 gene and the of the COQ6 of the COQ6 a the and The of the to to of the COQ6 and the to of The to to of the of the COQ6 by to of the of by and of the the as on by and and a of the and The the the and of and the of the are and as of Q and by and in of of by the of and the as The lipid the to and by a as The a of and a of the of to in the and to in the the the of to and to the The of by in of a The of of in by and and as and a COQ6 in of to an of to of as an to a of and the by of in of in by the COQ6 into the of the The COQ6 and and the and The and and into the and in The and in The in the of a of the and the The of mitochondria and to as The in to The and by a as mitochondria isolated a as of in and isolated mitochondria of the the mitochondria and as the by of to The to and by the of to a of of COQ6 and to the Coq6 polypeptide a to the of the an the The COQ6 the and The into the and and to a of by the by and into of the The the of the gene on on the to of COQ6 and a and The and into the to a protein a the The protein in the by and and to in of in to an and and mitochondria isolated and as by of mitochondria of in of and on The in a to the and the The and to matrix and membrane the by on by to the membrane the peripheral membrane and matrix as The by protein by the of protein the mitochondrial of by on and to and of as by to the the of the of and to a and in of the COQ6 in the coq6 complementation of mutants as a Q-deficient The respiratory to a in Q of to isolated mitochondria of the the and a and the the COQ6 gene by as and the in isolated and to the of a to of on the to as and The and the and a of the the of to grow on of the as a protein the of gene to of the COQ6 gene and of the the mutants and the the as an that a of the COQ6 in to a coq6 of the coq6 in to and a and and as by and not a by and the The to and of the on The a respiratory and that the COQ6 gene is not essential but is on nonfermentable carbon Q and of mutants in the of the in Q and is an intermediate in the Q biosynthetic and in in of the the in Q in a and in the of and lipid by as and accumulate a intermediate that in to as by a that as as of of of of and and of of to and and of of to the not as a to of the COQ6 and the and mutants and accumulate that is the that and The gene as a The gene as a to mutants accumulate and and mutants to grow on and and of Coq6 that are in a of and in an is in the of and in the of a to the of on the and and the of the in it that Coq6p functions in in Q of Coq6 The of the Coq6 polypeptide is in in and on the and the are Coq6 of and of of the Coq6 in on the and the The that as of the of is in the of and is in the of a to the of The are designated as and of Coq6p of mitochondrial Coenzyme in and The are in and of of in a the are side of the The the in mitochondrial matrix that are imported into as by an a and to the of the Coq6p is a mitochondrial an in mitochondrial of the Coq6 polypeptide mitochondria the in Coq6p and the of the protein to have a of as the protein and to of mitochondrial membrane the imported and to the The of Coq6p a mitochondrial membrane the of of Coq6p and mitochondrial and of of the in in in isolated as but a as to the mitochondria and in mitochondria in the of the the the mitochondria as in as in The and to by and and the of the and the of of of the of Coq6p of a protein Coq6p and the The protein as by the of the to on a nonfermentable carbon not and that the in mitochondria as an it in the and to the Coq6 in a a polypeptide of in and the Coq6 polypeptide that polypeptide in of the coq6 that the is of that Coq6p the mitochondria and Coq6p is a mitochondria to the membrane and of the by to the and membrane that Coq6p localizes to the membrane Coq6p in the inner mitochondria of and that Coq6p is the is as is the matrix and to Coq6p is a peripheral protein in the inner mitochondrial that Coq6p is into the as are the of and peripheral membrane membrane is is the inner membrane of the Coq6p and the the coq6 and the and by into mitochondrial mitochondrial and mitochondria to and to in the The and to a matrix protein in the and membrane protein mitochondria by on and mitochondria of the by and by as The Coq6p and of membrane protein protein inner membrane protein peripheral inner membrane and the of and matrix and and in of the COQ6 in the coq6 complementation of mutants as a Q-deficient The respiratory to a in Q of to isolated mitochondria of the the and a and the the COQ6 gene by as and the in isolated and to the of a to of on the to as and The and the and a of the the of to grow on of the as a protein the of The gene to of the COQ6 gene and of the the mutants and the the as COQ6 an that a of the COQ6 in to a coq6 of the coq6 in to and a and and as by and not a by and the The to and of the on The a respiratory and that the COQ6 gene is not essential but is on nonfermentable carbon Q and of mutants in the of the in Q and is an intermediate in the Q biosynthetic and in in of the the in Q in a and in the of and lipid by as and accumulate a intermediate that in to as by a that as as of of of of and and of of to and and of of to the not Coq6p as a to of the COQ6 and the and mutants and accumulate that is the that and The gene as a The gene as a to mutants accumulate and and mutants to grow on and and of Coq6 that are in a of and in an is in the of and in the of a to the of on the and and the of the in it that Coq6p functions in in Q of Coq6p of mitochondrial Coenzyme in and The are in and of of in a the are side of the The the in mitochondrial matrix that are imported into as by an a and to the of the Coq6p is a mitochondrial an in mitochondrial of the Coq6 polypeptide mitochondria the in Coq6p and the of the protein to have a of as the protein and to of mitochondrial membrane the imported and to the The of Coq6p a mitochondrial membrane the of of Coq6p and of of the of Coq6p of a protein Coq6p and the The protein as by the of the to on a nonfermentable carbon not and that the in mitochondria as an it in the and to the Coq6 in a a polypeptide of in and the Coq6 polypeptide that polypeptide in of the coq6 that the is of that Coq6p the mitochondria and Coq6p is a mitochondria to the membrane and of the by to the and membrane that Coq6p localizes to the membrane Coq6p in the inner mitochondria of and that Coq6p is the is as is the matrix and to Coq6p is a peripheral protein in the inner mitochondrial that Coq6p is into the as are the of and peripheral membrane membrane is coq6 mutants and the of the COQ6 gene. COQ6 is Q the coq6 and in coq6 and mutants, is and as a are respiratory on the COQ6 a mitochondrial protein Q to and the Coq6 polypeptide is imported into mitochondria Coenzyme in and of and Coq6p is to the matrix side of the inner membrane and cerevisiae is a of and and of the have as of the COQ6 gene into and of and into a in to the by contrast to of the COQ6 that of the eight is Q is in of Coq6p is as are the functions of and on to it is that Coq6p Coq6p and it that Coq6p functions in the of in previous have that is The polypeptide as a a of a a of of the mutants, that of the in Q of the in Q are and Coq6p of Coq6p to the to Coq6p are the of to and mutants accumulate it to the of is not of the mutants accumulate is that Coq6p the of to that the of to in is that previous a Q-deficient is it of the of Coq6p in the of Q of in of Coq6p that and a protein but a and the The in the in have that a of is Q a in of the eight in a in protein and and in in the of of lipid of coq6 mutants in the that mutants accumulate that an the of and a the of that the and mutants the of but and and and the of the in a The of in the coq6 mutants that Coq6p is of a the to a of the and unable to a polypeptide and we an of coq6 mutants and the of the COQ6 gene. COQ6 is Q the coq6 and in coq6 and mutants, is and as a are respiratory on the COQ6 a mitochondrial protein Q to and the Coq6 polypeptide is imported into mitochondria Coenzyme in and of and Coq6p is to the matrix side of the inner membrane and cerevisiae is a of and and of the have as of the COQ6 gene into and of and into a in to the by contrast to of the COQ6 that of the eight is Q is in The of Coq6p is as are the functions of and on to it is that Coq6p Coq6p and it that Coq6p functions in the of in previous have that is The polypeptide as a a of a a of of the mutants, that of the in Q of the in Q are and Coq6p of Coq6p to the to Coq6p are the of to and mutants accumulate it to the of is not of the mutants accumulate is that Coq6p the of to that the of to in is that previous a Q-deficient is it of the of Coq6p in the of Q of in of Coq6p that and a protein but a and the The in the in have that a of is Q a in of the eight in a in protein and and in in the of of lipid of coq6 mutants in the that mutants accumulate that an the of and a the of that the and mutants the of but and and and the of the in a The of in the coq6 mutants that Coq6p is of a the to a of the and unable to a polypeptide and we an of
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Gin et al. (2003) studied this question.
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