Tamura T, Lee D H, Osaka F, Fujiwara T, Shin S, Chung C H, Tanaka K, Ichihara A
Institute for Enzyme Research, University of Tokushima, Japan.
Biochim Biophys Acta. 1991 May 2;1089(1):95-102. doi: 10.1016/0167-4781(91)90090-9.
Proteasomes are multicatalytic proteinase complexes consisting of a set of non-identical polypeptide components. Of these multiple components, the nucleotide sequences of five major subunits (named HC2, HC3, HC5, HC8 and HC9) of human proteasomes have been determined from recombinant cDNA clones by screening a human HepG2 hepatoblastoma cell cDNA library with rat proteasome cDNAs isolated previously as probes. The polypeptides deduced from their nucleotide sequences consisted of 263, 234, 241, 255 and 261 amino acid residues with calculated molecular weights of 29,554, 25,897, 26,487, 28,431 and 29,482, respectively, which are encoded by single independent genes. The primary structures of these subunits of human proteasomes closely resemble those of their rat counterparts and show considerably high inter-subunit homology, although the homology of HC5 is relatively low. These findings, together with the structural similarities of other eukaryotic proteasomes including those of Drosophila and yeast (Saccharomyces cerevisiae) support and extend the previously proposed concept that eukaryotic proteasome genes form a multi-gene family with the same evolutionary origin.
蛋白酶体是由一组不同的多肽成分组成的多催化蛋白酶复合物。在这些多种成分中，通过用先前分离的大鼠蛋白酶体cDNA作为探针筛选人肝癌细胞系HepG2 cDNA文库，已从重组cDNA克隆中确定了人蛋白酶体五个主要亚基（命名为HC2、HC3、HC5、HC8和HC9）的核苷酸序列。从其核苷酸序列推导的多肽分别由263、234、241、255和261个氨基酸残基组成，计算分子量分别为29,554、25,897、26,487、28,431和29,482，它们由单个独立基因编码。人蛋白酶体这些亚基的一级结构与其大鼠对应物的一级结构非常相似，并且显示出相当高的亚基间同源性，尽管HC5的同源性相对较低。这些发现，连同包括果蝇和酵母（酿酒酵母）在内的其他真核生物蛋白酶体的结构相似性，支持并扩展了先前提出的概念，即真核生物蛋白酶体基因形成具有相同进化起源的多基因家族。
