Jakubowski H, Goldman E
Department of Microbiology and Molecular Genetics, UMDNJ-New Jersey Medical School, Newark 07103.
FEBS Lett. 1993 Feb 15;317(3):237-40. doi: 10.1016/0014-5793(93)81283-6.
Homocysteine thiolactone is a product of an error-editing reaction, catalyzed by Escherichia coli and Saccharomyces cerevisiae methionyl-tRNA synthetases, which prevents incorporation of homocysteine into tRNA and protein both in vitro and in vivo. Here, homocysteine thiolactone is also shown to be synthesized by cultured mammalian cells such as human cervical carcinoma (HeLa), mouse renal adenocarcinoma (RAG), and Chinese hamster ovary (CHO) cells labeled with [35S]methionine, but not by normal human and mouse (Balb/c 3T3) fibroblasts. A temperature-sensitive methionyl-tRNA synthetase mutant of CHO cells, Met-1, does not make the thiolactone at the non-permissive temperature. The data indicate that methionyl-tRNA synthase is involved in synthesis of homocysteine thiolactone in CHO cells, thereby extending this important proofreading mechanism to mammalian cells.
同型半胱氨酸硫内酯是一种错误编辑反应的产物，由大肠杆菌和酿酒酵母甲硫氨酰 - tRNA合成酶催化，该反应在体外和体内均能阻止同型半胱氨酸掺入tRNA和蛋白质中。在此，还表明同型半胱氨酸硫内酯可由培养的哺乳动物细胞合成，如用[35S]甲硫氨酸标记的人宫颈癌（HeLa）细胞、小鼠肾腺癌（RAG）细胞和中国仓鼠卵巢（CHO）细胞，但正常人和小鼠（Balb/c 3T3）成纤维细胞则不能合成。CHO细胞的温度敏感型甲硫氨酰 - tRNA合成酶突变体Met - 1在非允许温度下不产生硫内酯。数据表明甲硫氨酰 - tRNA合成酶参与了CHO细胞中同型半胱氨酸硫内酯的合成，从而将这一重要的校对机制扩展到了哺乳动物细胞。
