Fiermonte Giuseppe, Paradies Eleonora, Todisco Simona, Marobbio Carlo M T, Palmieri Ferdinando
Department of Pharmaco-Biology, Laboratory of Biochemistry and Molecular Biology, University of Bari, Italy.
J Biol Chem. 2009 Jul 3;284(27):18152-9. doi: 10.1074/jbc.M109.014118. Epub 2009 May 8.
Mitochondrial carriers are a family of proteins that transport metabolites, nucleotides, and cofactors across the inner mitochondrial membrane thereby connecting cytosolic and matrix functions. The essential cofactor coenzyme A (CoA) is synthesized outside the mitochondrial matrix and therefore must be transported into mitochondria where it is required for a number of fundamental processes. In this work we have functionally identified and characterized SLC25A42, a novel human member of the mitochondrial carrier family. The SLC25A42 gene (Haitina, T., Lindblom, J., Renström, T., and Fredriksson, R., 2006, Genomics 88, 779-790) was overexpressed in Escherichia coli, purified, and reconstituted into phospholipid vesicles. Its transport properties, kinetic parameters, and targeting to mitochondria demonstrate that SLC25A42 protein is a mitochondrial transporter for CoA and adenosine 3',5'-diphosphate. SLC25A42 catalyzed only a counter-exchange transport, exhibited a high transport affinity for CoA, dephospho-CoA, ADP, and adenosine 3',5'-diphosphate, was saturable and inhibited by bongkrekic acid and other inhibitors of mitochondrial carriers to various degrees. The main physiological role of SLC25A42 is to import CoA into mitochondria in exchange for intramitochondrial (deoxy)adenine nucleotides and adenosine 3',5'-diphosphate. This is the first time that a mitochondrial carrier for CoA and adenosine 3',5'-diphosphate has been characterized biochemically.
线粒体载体是一类蛋白质家族，可跨线粒体内膜转运代谢物、核苷酸和辅因子，从而连接胞质和基质功能。必需辅因子辅酶A（CoA）在线粒体基质外合成，因此必须转运至线粒体中，许多基本过程都需要它。在这项研究中，我们从功能上鉴定并表征了线粒体载体家族的一个新的人类成员SLC25A42。SLC25A42基因（Haitina, T., Lindblom, J., Renström, T., and Fredriksson, R., 2006, Genomics 88, 779 - 790）在大肠杆菌中过表达、纯化并重组到磷脂囊泡中。其转运特性、动力学参数以及定位于线粒体表明，SLC25A42蛋白是CoA和3',5'-二磷酸腺苷的线粒体转运体。SLC25A42仅催化反向交换转运，对CoA、脱磷酸CoA、ADP和3',5'-二磷酸腺苷表现出高转运亲和力，具有饱和性，并受到邦克雷酸和其他线粒体载体抑制剂的不同程度抑制。SLC25A42的主要生理作用是将CoA导入线粒体，以交换线粒体内的（脱氧）腺嘌呤核苷酸和3',5'-二磷酸腺苷。这是首次对CoA和3',5'-二磷酸腺苷的线粒体载体进行生化表征。
