Kang D, Nishida J, Iyama A, Nakabeppu Y, Furuichi M, Fujiwara T, Sekiguchi M, Takeshige K
Department of Biochemistry, Kyushu University School of Medicine, Fukuoka, Japan.
J Biol Chem. 1995 Jun 16;270(24):14659-65. doi: 10.1074/jbc.270.24.14659.
We examined the intracellular distribution of 8-oxo-dGTPase (8-oxo-7,8-dihydrodeoxyguanosine triphosphatase) encoded by the MTH1 gene, a human mutator homologue. The activity of 8-oxo-dGTPase mainly located in cytosolic and mitochondrial soluble fractions of Jurkat cells, a human T-cell leukemia line. Electron microscopic immunocytochemistry, using a specific antibody against MTH1 protein, showed localization of MTH1 protein in the mitochondrial matrix. Activity in the mitochondria accounted for about 4% of the total activity. The specific activity in the mitochondrial soluble fraction (8093 units/mg protein) was as high as that in the cytosolic fraction (8111 unit/mg protein). The 8-oxo-dGTPase activities in cytosolic and mitochondrial soluble fractions co-eluted with MTH1 protein by anion-exchange chromatography, and the molecular mass of the mitochondrial MTH1 protein was much the same as that of the cytosolic MTH1 protein (about 18 kDa). HeLa cells expressing MTH1 cDNA showed an increased cytoplasmic signal together with a weak signal in the nucleus in in situ immunostaining of MTH1 protein, and the overexpressed MTH1 protein was recovered from both cytosolic and mitochondrial fractions. Thus, the 8-oxo-dGTPase encoded by MTH1 gene is localized in mitochondrial and cytosol.
我们研究了由人类突变同源基因MTH1编码的8-氧代-dGTP酶（8-氧代-7,8-二氢脱氧鸟苷三磷酸酶）的细胞内分布。8-氧代-dGTP酶的活性主要位于人T细胞白血病细胞系Jurkat细胞的胞质和线粒体可溶性部分。使用针对MTH1蛋白的特异性抗体进行的电子显微镜免疫细胞化学显示，MTH1蛋白定位于线粒体基质中。线粒体中的活性约占总活性的4%。线粒体可溶性部分的比活性（8093单位/毫克蛋白）与胞质部分的比活性（8111单位/毫克蛋白）一样高。通过阴离子交换色谱法，胞质和线粒体可溶性部分的8-氧代-dGTP酶活性与MTH1蛋白共洗脱，线粒体MTH1蛋白的分子量与胞质MTH1蛋白的分子量大致相同（约18 kDa）。在MTH1蛋白的原位免疫染色中，表达MTH1 cDNA的HeLa细胞在细胞质中显示出增强的信号，同时在细胞核中显示出微弱的信号，并且从胞质和线粒体部分都回收了过表达的MTH1蛋白。因此，由MTH1基因编码的8-氧代-dGTP酶定位于线粒体和细胞质中。
