tailieunhanh - Báo cáo khoa học: Saccharomyces cerevisiae coq10 null mutants are responsive to antimycin A

Deletion ofCOQ10in Saccharomyces cerevisiaeelicits a respiratory defect characterized by the absence of cytochrome creduction, which is correct-able by the addition of exogenous diffusible coenzyme Q2. Unlike other coq mutants with hampered coenzyme Q6 (Q6 ) synthesis, coq10 mutants have near wild-type concentrations of Q6. | Saccharomyces cerevisiae coq10 null mutants are responsive to antimycin A Cleverson Busso1 Erich B. Tahara2 Renata Ogusucu2 Ohara Augusto2 Jose Ribamar Ferreira-Junior3 Alexander Tzagoloff4 Alicia J. Kowaltowski2 and Mario H. Barros1 1 Departamento de Microbiologia Institute de Ciencias Biomedicas Universidade de Sao Paulo Brazil 2 Departmento de Bioquimica Instituto de Quimica Universidade de Sao Paulo Brazil 3 Escola de Artes Ciencias e Humanidades Universidade de Sao Paulo Brazil 4 Department of BiologicalSciences Columbia University New York NY USA Keywords coenzyme Q mitochondria Saccharomyces cerevisiae Correspondence M. H. Barros Departamento de Microbiologia Instituto de Ciencias Biomedicas Universidade de Sao Paulo Av. Professor Lineu Prestes 1374 05508-900 Sao Paulo Brazil Fax 55 11 30917354 Tel 55 11 30918456 E-mail mariohb@ Received 16 June 2010 revised 3 August 2010 accepted 3 September 2010 doi Deletion of COQ10 in Saccharomyces cerevisiae elicits a respiratory defect characterized by the absence of cytochrome c reduction which is correctable by the addition of exogenous diffusible coenzyme Q2. Unlike other coq mutants with hampered coenzyme Q6 Q6 synthesis coq10 mutants have near wild-type concentrations of Q6. In the present study we used Q-cycle inhibitors of the coenzyme QH2-cytochrome c reductase complex to assess the electron transfer properties of coq10 cells. Our results show that coq10 mutants respond to antimycin A indicating an active Q-cycle in these mutants even though they are unable to transport electrons through cytochrome c and are not responsive to myxothiazol. EPR spectroscopic analysis also suggests that wild-type and coq10 mitochondria accumulate similar amounts of Q6 semiquinone despite a lower steady-state level of coenzyme QH2-cytochrome c reductase complex in the coq10 cells. Confirming the reduced respiratory chain state in coq10 cells we found that the expression of the Aspergillus .