Whanger P D, Deagen J T, Beilstein M A
Department of Agricultural Chemistry, Oregon State University, Corvallis 97331.
Experientia Suppl. 1987;52:281-7. doi: 10.1007/978-3-0348-6784-9_23.
Since the assumed metallothionein (MT) fractions from testis did not respond to cadmium and zinc exposure like MT in other tissues, they were purified using gel filtration and ion exchange resins to determine if they were indeed MT or other proteins. The major amino acids were found to be aspartate, glutamate and glycine with a low cysteine (less than 3%) content. The amino acid content is remarkably similar to a low molecular weight (MW) cadmium-binding protein isolated from oysters with properties unlike MT. Selenium has been shown to be present in a low MW protein called the G protein in various tissues including the testis. The major amino acids in a partially purified preparation were found to be aspartate, glutamate, glycine and lysine with a low methionine (about 2.5%) but a very low cysteine (less than 0.3%) content. The selenium is present in this protein as selenocysteine. The metabolic significance of this selenoprotein is not known, but it should be indicated that selenium will alter the binding of cadmium in testicular proteins.
由于睾丸中假定的金属硫蛋白（MT）组分对镉和锌暴露的反应不像其他组织中的MT那样，因此使用凝胶过滤和离子交换树脂对它们进行纯化，以确定它们是否确实是MT或其他蛋白质。发现主要氨基酸为天冬氨酸、谷氨酸和甘氨酸，半胱氨酸含量较低（低于3%）。氨基酸含量与从牡蛎中分离出的一种低分子量（MW）镉结合蛋白非常相似，其性质与MT不同。已证明硒存在于包括睾丸在内的各种组织中的一种名为G蛋白的低分子量蛋白质中。在部分纯化的制剂中发现主要氨基酸为天冬氨酸、谷氨酸、甘氨酸和赖氨酸，甲硫氨酸含量低（约2.5%），但半胱氨酸含量极低（低于0.3%）。硒以硒代半胱氨酸的形式存在于该蛋白质中。这种硒蛋白的代谢意义尚不清楚，但应该指出的是，硒会改变睾丸蛋白质中镉的结合。
