Tamura T, Shimbara N, Aki M, Ishida N, Bey F, Scherrer K, Tanaka K, Ichihara A
Institute for Enzyme Research, School of Medicine, University of Tokushima.
J Biochem. 1992 Oct;112(4):530-4. doi: 10.1093/oxfordjournals.jbchem.a123933.
Proteasomes (multi-protease complexes) are composed of approximately 15 non-identical subunits of similar sizes (molecular weight = 21-32 kDa), but different charges (isoelectric point = 4-9). Previously, we deduced the primary structures of 6 subunits of rat proteasomes by recombinant DNA techniques. In this paper we report the nucleotide sequences of 4 other subunits, rIOTA, rZETA, rDELTA, and rRING12, determined from cDNA clones isolated by screening a rat H4TG hepatoma cell cDNA library with the cDNAs of their human counterparts as probes. The polypeptides deduced from their nucleotide sequences consisted of 246, 241, 202, and 219 amino acid residues with calculated molecular weights of 27,399, 26,391, 21,649, and 23,324, and calculated isoelectric points of 6.37, 4.65, 4.84, and 4.70, respectively. These results and previous findings indicate that the primary structures of the subunits of rat proteasomes show considerably high inter-subunit homology, but can be classified into apparently distinct sub-groups, suggesting that rat proteasome genes form a multi-gene family with the same evolutionary origin, but have diverged during evolution to acquire possibly subunit-specific functions.
蛋白酶体（多蛋白酶复合物）由大约15个大小相似（分子量=21 - 32 kDa）但电荷不同（等电点=4 - 9）的不同亚基组成。此前，我们通过重组DNA技术推导了大鼠蛋白酶体6个亚基的一级结构。在本文中，我们报告了另外4个亚基rIOTA、rZETA、rDELTA和rRING12的核苷酸序列，这些序列是通过用人相应亚基的cDNA作为探针筛选大鼠H4TG肝癌细胞cDNA文库分离得到的cDNA克隆确定的。从它们的核苷酸序列推导的多肽分别由246、241、202和219个氨基酸残基组成，计算分子量分别为27,399、26,391、21,649和23,324，计算等电点分别为6.37、4.65、4.84和4.70。这些结果和先前的发现表明，大鼠蛋白酶体亚基的一级结构显示出相当高的亚基间同源性，但可分为明显不同的亚组，这表明大鼠蛋白酶体基因形成了一个具有相同进化起源的多基因家族，但在进化过程中发生了分化，以获得可能的亚基特异性功能。
