Mizutani T, Hitaka T
Faculty of Pharmaceutical Sciences, Nagoya City University, Japan.
FEBS Lett. 1988 May 9;232(1):243-8. doi: 10.1016/0014-5793(88)80425-3.
This study has been undertaken in order to elucidate the mechanisms of incorporation of Se into glutathione peroxidase (GSHPx), in which selenocysteine corresponds to the opal termination codon UGA on the mRNA. We studied the above mechanisms using an opal suppressor tRNA, prepared from bovine liver, and casein as a model protein for the GSHPx apo-enzyme which might contain phosphoserine. The results showed that opal suppressor tRNA did not accept selenocysteine (lower than 0.1 mmol/mol) under the standard conditions. A trace amount of phosphoseryl-tRNA was converted to selenocysteyl-tRNA by incubation with H2Se and some enzymes. Meanwhile, a number of phosphoserine residues in casein were converted to selenocysteine residues by incubation with H2Se and enzymes. These results suggest that opal suppressor tRNA plays a role in synthesizing GSHPx via co- and/or post-translational mechanisms.
进行本研究是为了阐明硒掺入谷胱甘肽过氧化物酶（GSHPx）的机制，其中硒代半胱氨酸对应于mRNA上的乳白终止密码子UGA。我们使用从牛肝制备的乳白抑制tRNA和酪蛋白作为可能含有磷酸丝氨酸的GSHPx脱辅基酶的模型蛋白来研究上述机制。结果表明，在标准条件下，乳白抑制tRNA不接受硒代半胱氨酸（低于0.1 mmol/mol）。通过与H2Se和一些酶孵育，微量的磷酸丝氨酰-tRNA被转化为硒代半胱氨酰-tRNA。同时，通过与H2Se和酶孵育，酪蛋白中的许多磷酸丝氨酸残基被转化为硒代半胱氨酸残基。这些结果表明，乳白抑制tRNA通过共翻译和/或翻译后机制在合成GSHPx中发挥作用。
