Selenium Biochemistry

硒磷酸(SEP)是合成多种硒酶所需的富含能量的硒化合物，是由三磷酸腺苷(ATP)合成的硒合成酶(SPS)和无机形式的硒形成的。纯化的酶含有结合的紫外线吸收发色团，其特征由马特·沃尔夫博士表征。特殊的硒转运蛋白参与向SPS提供特异性的硒，从而将细胞内的硒水平维持在毒性水平以下。某些类可以利用硒半胱氨酸作为底物的递送蛋白，即硒半胱氨酸裂解酶，包括来自大肠杆菌的三种NIFS相关蛋白质和一种来自凡尼氏甲烷球菌的蛋白质，万氏甲烷球菌是一种厌氧生物，特别富含硒酶和硒蛋白质生物合成所需的因子。 先前从vannielii中分离到一个与无机硒反应的硒结合蛋白，并分离、克隆了该蛋白的编码基因，并在大肠杆菌中进行了表达。对分离的重组蛋白在兔体内产生的抗体进行纯化，并由Renee Piells用于制备抗体柱。采用抗体柱技术，有效地纯化了vannielii天然硒结合蛋白和大肠杆菌重组蛋白。Kemberly Patteson对高度疏水的硒结合蛋白的物理性质的详细研究有助于解释天然形式和重组形式保留结合硒的能力。该蛋白质由8.8 kDa亚基组成，包含81个氨基酸，非常不易解离，特别是在热处理的情况下。有证据表明，存在于每个亚基中的单一半胱氨酸残基参与了硒的结合。该蛋白在将硒输送到硒磷酸合成酶中的潜在作用正在研究中。获得结晶形式的硒磷酸合成酶的尝试仍在继续，作为一种定位蛋白质上经历ATP磷酸化的位置的方法。马特·沃尔夫正在继续研究紫外线吸收发色团的身份及其作用。 用~(75)Se研究了单细胞真核生物Dictyostellium的硒代谢。作为二聚体在凝胶上迁移的一种突出的放射性蛋白质已经被部分纯化，并正在尝试确定其身份。这种阿米巴易于在普通类型的液体介质中培养，这使它成为研究真核生物中硒酶生物合成的一个有吸引力的生物。

Selenophosphate (SeP), the energy-rich Se compound required for synthesis of many selenoenzymes is formed by selenophosphate synthetase (SPS) from ATP and an inorganic form of Se. The purified enzyme contains a bound UV absorbing chromophore characterized by Dr. Matt Wolfe. The participation of specialized selenium delivery proteins to furnish Se specifically to SPS serves to maintain intracellular levels of selenium below toxic levels. Certain classes of delivery proteins that can utilize selenocysteine as substrate, selenocysteine lyases, include three NifS related proteins from E. coli and one from Methanococcus vannielii, an anaerobic organism that is particularly rich in selenoenzymes and factors required for selenoprotein biosynthesis. A selenium-binding protein that reacts with inorganic selenium was isolated previously from M. vannielii and the gene encoding this protein was isolated, cloned, and expressed in E. coli. Antibodies produced in rabbits to the isolated recombinant protein were purified and used by Renee Pierce to prepare antibody columns. The native selenium binding protein from M. vannielii and the recombinant protein from E. coli were purified effectively using the antibody column technique. Detailed studies on the physical properties of the highly hydrophobic selenium-binding protein by Kemberly Patteson helped to explain the ability of the native and recombinant forms to retain bound selenium. The protein which consists of 8.8 kDa subunits that contain 81 amino acids is very resistant to dissociation, especially by heat treatment. There is evidence that the single cysteine residue present in each subunit participates in selenium-binding. A potential role of the protein in the delivery of selenium to selenophosphate synthetase is under investigation. Attempts to obtain selenophosphate synthetase in crystalline form are continuing as a means of locating the site on the protein that undergoes phosphorylation by ATP. The identity of the UV absorbing chromophore and its role are continuing to be investigated by Matt Wolfe. Selenium metabolism in a single celled eukaryotic organism, Dictyostellium, was investigated using 75Se by Thressa Stadtman. A prominent radioactive protein that migrated on gels as a dimer has been partially purified and attempts are under way to determine its identity. The ease of culture of this amoeba in ordinary types of liquid media make it an attractive organism for study of selenoenzyme biosynthesis in eukaryotes.