Slocinska Malgorzata, Szewczyk Adam, Hryniewiecka Lilla, Kmita Hanna
Department of Bioenergetics, Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, Poznań, Poland.
Acta Biochim Pol. 2004;51(4):953-62.
Benzodiazepine binding sites were studied in mitochondria of unicellular eukaryotes, the amoeba Acathamoeba castellanii and the yeast Saccharomyces cerevisiae, and also in rat liver mitochondria as a control. For that purpose we applied Ro5-4864, a well-known ligand of the mitochondrial benzodiazepine receptor (MBR) present in mammalian mitochondria. The levels of specific [(3)H]Ro5-4864 binding, the dissociation constant (K(D)) and the number of [(3)H]Ro5-4864 binding sites (B(max)) determined for fractions of the studied mitochondria indicate the presence of specific [(3)H]Ro5-4864 binding sites in the outer membrane of yeast and amoeba mitochondria as well as in yeast mitoplasts. Thus, A. castellanii and S. cerevisiae mitochondria, like rat liver mitochondria, contain proteins able to bind specifically [(3)H]Ro5-4864. Labeling of amoeba, yeast and rat liver mitochondria with [(3)H]Ro5-4864 revealed proteins identified as the voltage dependent anion selective channel (VDAC) in the outer membrane and adenine nucleotide translocase (ANT) in the inner membrane. Therefore, the specific MBR ligand binding is not confined only to mammalian mitochondria and is more widespread within the eukaryotic world. However, it can not be excluded that MBR ligand binding sites are exploited efficiently only by higher multicellular eukaryotes. Nevertheless, the MBR ligand binding sites in mitochondria of lower eukaryotes can be applied as useful models in studies on mammalian MBR.
在单细胞真核生物的线粒体中研究了苯二氮䓬结合位点，这些单细胞真核生物包括阿米巴变形虫卡氏棘阿米巴和酿酒酵母，同时也研究了大鼠肝脏线粒体作为对照。为此，我们应用了Ro5 - 4864，它是哺乳动物线粒体中存在的线粒体苯二氮䓬受体（MBR）的一种知名配体。对所研究线粒体各部分测定的特异性[(3)H]Ro5 - 4864结合水平、解离常数（K(D)）和[(3)H]Ro5 - 4864结合位点数量（B(max)）表明，酵母和阿米巴线粒体的外膜以及酵母线粒体膜间隙中存在特异性[(3)H]Ro5 - 4864结合位点。因此，卡氏棘阿米巴和酿酒酵母的线粒体，与大鼠肝脏线粒体一样，含有能够特异性结合[(3)H]Ro5 - 4864的蛋白质。用[(3)H]Ro5 - 4864标记阿米巴、酵母和大鼠肝脏线粒体后，发现外膜中被鉴定为电压依赖性阴离子选择性通道（VDAC）的蛋白质以及内膜中被鉴定为腺嘌呤核苷酸转位酶（ANT）的蛋白质。所以，特异性MBR配体结合并不局限于哺乳动物线粒体，在真核生物界更为广泛。然而，不能排除只有高等多细胞真核生物才能有效利用MBR配体结合位点。尽管如此，低等真核生物线粒体中的MBR配体结合位点可作为研究哺乳动物MBR的有用模型。
