The covalent structure of mitochondrial aspartate aminotransferase from chicken. Identification of segments of the polypeptide chain invariant specifically in the mitochondrial isoenzyme.
The covalent structure of mitochondrial aspartate aminotransferase from chicken. Identification of segments of the polypeptide chain invariant specifically in the mitochondrial isoenzyme.
复制标题
鸡线粒体天冬氨酸转氨酶的共价结构。
DOI：
10.1016/s0021-9258(18)32129-x
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发表时间：
1983
期刊：
影响因子：
--
通讯作者：
P. Christen
中科院分区：
文献类型：
--
作者：
U. Graf;K. Wilson;P. Christen
报道了鸡线粒体天冬氨酸转氨酶的一级结构。该酶是相同亚基的二聚体。每个亚基含有401个氨基酸残基；计算得出的apoform亚基分子量为44,866。与鸡的同源胞质同工酶的序列同一性程度为46%。对猪和鸡的线粒体和胞质同工酶的一级结构进行比较表明，40% 的残基是不变的。鸡和猪线粒体和胞质同工酶的种间序列同一性程度（分别为 86% 和 83%）明显超过鸡（46%）或猪（48%）线粒体和胞质天冬氨酸转氨酶之间的种内同一性。根据这些值，天冬氨酸转氨酶祖先基因的复制估计发生在大约 10 亿年前，即真核细胞出现时。通过序列比较，可以鉴定在系统发育进化过程中线粒体同工酶中特异保守的氨基酸残基和多肽链片段。这些片段约占总多肽链的三分之一，并且似乎聚集在某个表面区域。该簇携带过量的带正电荷的残基，其超过了胞质（pI约6）和线粒体同工酶（pI约9）之间的总电荷差。
The primary structure of mitochondrial aspartate aminotransferase from chicken is reported. The enzyme is a dimer of identical subunits. Each subunit contains 401 amino acid residues; the calculated subunit molecular weight of the apoform is 44,866. The degree of sequence identity with the homologous cytosolic isoenzyme from chicken is 46%. A comparison of the primary structures of the mitochondrial and the cytosolic isoenzyme from pig and chicken shows that 40% of all residues are invariant. The degree of interspecies sequence identity both of the mitochondrial and the cytosolic isoenzyme from chicken and pig (86% and 83%, respectively) markedly exceeds that of the intraspecies identity between mitochondrial and cytosolic aspartate aminotransferase in chicken (46%) or in pig (48%). Based on these values, the duplication of the aspartate aminotransferase ancestral gene is estimated to have occurred approximately 1000 million years ago, i.e. at the time of the emergence of eukaryotic cells. By sequence comparison it is possible to identify amino acid residues and segments of the polypeptide chain that have been conserved specifically in the mitochondrial isoenzyme during phylogenetic evolution. These segments comprise about a third of the total polypeptide chain and appear to cluster in a certain surface region. The cluster carries an excess of positively charged residues which exceeds the overall charge difference between the cytosolic (pI approximately 6) and the mitochondrial isoenzyme (pI approximately 9).