RESUMO
The UbiB protein kinase-like (PKL) family is widespread, comprising one-quarter of microbial PKLs and five human homologs, yet its biochemical activities remain obscure. COQ8A (ADCK3) is a mammalian UbiB protein associated with ubiquinone (CoQ) biosynthesis and an ataxia (ARCA2) through unclear means. We show that mice lacking COQ8A develop a slowly progressive cerebellar ataxia linked to Purkinje cell dysfunction and mild exercise intolerance, recapitulating ARCA2. Interspecies biochemical analyses show that COQ8A and yeast Coq8p specifically stabilize a CoQ biosynthesis complex through unorthodox PKL functions. Although COQ8 was predicted to be a protein kinase, we demonstrate that it lacks canonical protein kinase activity in trans. Instead, COQ8 has ATPase activity and interacts with lipid CoQ intermediates, functions that are likely conserved across all domains of life. Collectively, our results lend insight into the molecular activities of the ancient UbiB family and elucidate the biochemical underpinnings of a human disease.
Assuntos
Comportamento Animal , Ataxia Cerebelar/enzimologia , Cerebelo/enzimologia , Proteínas Mitocondriais/deficiência , Músculo Esquelético/enzimologia , Ubiquinona/deficiência , Animais , Células COS , Ataxia Cerebelar/genética , Ataxia Cerebelar/fisiopatologia , Ataxia Cerebelar/psicologia , Cerebelo/fisiopatologia , Cerebelo/ultraestrutura , Chlorocebus aethiops , Modelos Animais de Doenças , Tolerância ao Exercício , Feminino , Predisposição Genética para Doença , Células HEK293 , Humanos , Metabolismo dos Lipídeos , Masculino , Aprendizagem em Labirinto , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteínas Mitocondriais/química , Proteínas Mitocondriais/genética , Modelos Moleculares , Atividade Motora , Força Muscular , Músculo Esquelético/fisiopatologia , Fenótipo , Ligação Proteica , Conformação Proteica , Proteômica/métodos , Reconhecimento Psicológico , Teste de Desempenho do Rota-Rod , Saccharomyces cerevisiae/enzimologia , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Convulsões/enzimologia , Convulsões/genética , Convulsões/fisiopatologia , Relação Estrutura-Atividade , Fatores de Tempo , Transfecção , Ubiquinona/química , Ubiquinona/genéticaRESUMO
Coenzyme Q (Q) is an electron transporter in the respiratory chain and a lipid-soluble antioxidant that decreases in humans with age. Here we show that 4-nitrobenzoate inhibited 4-hydroxybenzoate:polyprenyl transferase (Coq2) in a competitive manner and dose-dependently decreased Q in mammalian cells without accumulation of Q intermediates. As 4-nitrobenzoate neither interfered with mitochondrial respiration nor induced oxidative stress, it should prove a valuable tool for studies on both Q deficiency and Q supplementation.