Hill K E, Lloyd R S, Yang J G, Read R, Burk R F
Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee 37232.
J Biol Chem. 1991 Jun 5;266(16):10050-3.
Selenoprotein P is a plasma protein recently purified and characterized as containing 7.5 +/- 1.0 selenium atoms/molecule as selenocysteine. In rats maintained on a defined diet containing nutritionally adequate amounts of selenate as the sole selenium source, over half the selenium in plasma is accounted for by selenoprotein P. Its cDNA has been cloned from a rat liver library and sequenced. The sequence is highly unusual, containing 10 TGA codons in its open reading frame prior to the TAA termination codon. TGA designates selenocysteine in other selenoproteins, and limited peptide sequencing that included the amino acids encoded by two of the TGA codons verified that they correspond to selenocysteine. The deduced 366-amino acid sequence is histidine- and cysteine-rich and contains 9 of its selenocysteines in the terminal 122 amino acids. Comparison of the deduced amino acid sequence of selenoprotein P with those of other selenoprotein reveals no significant similarities. Selenoprotein P represents a new class of selenoproteins and is the first protein described with more than 1 selenocysteine in a single polypeptide chain. The primary structure of selenoprotein P suggests that it might be responsible for some of the antioxidant properties of selenium.
硒蛋白P是一种最近纯化并鉴定的血浆蛋白，其每个分子含有7.5±1.0个作为硒代半胱氨酸的硒原子。在以营养充足的硒酸盐作为唯一硒源的特定饮食喂养的大鼠中，血浆中一半以上的硒由硒蛋白P构成。其cDNA已从大鼠肝脏文库中克隆并测序。该序列非常独特，在TAA终止密码子之前的开放阅读框中含有10个TGA密码子。在其他硒蛋白中，TGA代表硒代半胱氨酸，对包括两个TGA密码子编码的氨基酸在内的有限肽段测序证实它们对应于硒代半胱氨酸。推导的366个氨基酸的序列富含组氨酸和半胱氨酸，其9个硒代半胱氨酸位于末端122个氨基酸中。将硒蛋白P推导的氨基酸序列与其他硒蛋白的序列进行比较，未发现明显相似性。硒蛋白P代表一类新的硒蛋白，是首个被描述的在单条多肽链中含有不止一个硒代半胱氨酸的蛋白质。硒蛋白P的一级结构表明它可能负责硒的一些抗氧化特性。
