Molecular biological and biochemical characterization of the human type 2 selenodeiodinase.
Molecular biological and biochemical characterization of the human type 2 selenodeiodinase.
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DOI：
10.1210/endo.137.8.8754756
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发表时间：
1996-08
期刊：
影响因子：
4.8
通讯作者：
D. Salvatore;T. Bartha;J. Harney;P. Larsen
中科院分区：
文献类型：
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作者：
D. Salvatore;T. Bartha;J. Harney;P. Larsen
2型脱碘酶（D2）是一种低K(m)碘甲状腺原氨酸脱碘酶，催化从T4或rT3的酚环上去除单个碘。我们对Genethon （Z44085）从人类婴儿大脑cDNA文库中制备的部分互补DNA （cDNA）克隆（2.1千碱基）进行了测序和亚克隆。该开放阅读框编码一个全长31 kDa、含有273个氨基酸的蛋白，与Rana catesbeiana D2蛋白的相似性超过70%。cDNA的瞬时表达在293-HEK细胞中产生低K(m) （T4为5 nM， rT3为8 nM）丙基硫脲嘧啶和金硫葡萄糖抗性5'-脱碘酶。人类D2，像人类1型（D1）和3型（D3）脱碘酶一样，是一种硒酶，这一点可以证明：1)在帧内存在两个UGA密码子（位置133和266），2)在D2 cdna转染的细胞中合成一个31 kda 75selable标记的蛋白，以及3)需要一个3'-硒代半胱氨酸结合序列元件来翻译。与D1和D3不同，我们无法用n -溴乙酰[125I]T3或-T4共价标记过表达的D2。我们发现人类D2信使RNA有7-8千碱基，在大脑、胎盘中表达，令人惊讶的是，在心脏和骨骼肌中也表达。2型脱碘酶活性也存在于人类骨骼肌中。这些结果表明D2具有区别于其他两种硒代去碘酶的独特特征。D2在肌肉中的表达表明，它可能在外周和细胞内T3的产生中发挥作用。
Type 2 deiodinase (D2) is a low K(m) iodothyronine deiodinase that catalyzes the removal of a single iodine from the phenolic ring of T4 or rT3. We sequenced and subcloned the open reading frame from a partial complementary DNA (cDNA) clone (2.1 kilobases) prepared by Genethon (Z44085) from a human infant brain cDNA library. The open reading frame encodes a putative 273-amino acid protein of 31 kDa with greater than 70% similarity to the Rana catesbeiana D2 protein. Transient expression of the cDNA produces a low K(m) (5 nM for T4; 8 nM for rT3) propylthiouracil- and gold thioglucose-resistant 5'-deiodinase in 293-HEK cells. Human D2, like human type 1 (D1) and type 3 (D3) deiodinases, is a selenoenzyme, as evidenced by 1) the presence of two in-frame UGA codons (positions 133 and 266), 2) the synthesis of a 31-kDa 75Selabeled protein in D2 cDNA-transfected cells, and 3) the requirement for a 3'-selenocysteine incorporation sequence element for its translation. Unlike D1 and D3, we were not able to covalently label overexpressed D2 with N-bromoacetyl [125I]T3 or -T4. We found that the human D2 messenger RNA is 7-8 kilobases and is expressed in brain, placenta, and, surprisingly, cardiac and skeletal muscle. Type 2 deiodinase activity was also present in human skeletal muscle. These results indicate that there are unique features of D2 that distinguish it from the two other selenodeiodinases. The expression of D2 in muscle suggests that it could play a role in peripheral, as well as intracellular, T3 production.