Mouse extracellular superoxide dismutase: Primary structure, tissue-specific gene expression, chromosomal localization, and lung in situ hybridization
Mouse extracellular superoxide dismutase: Primary structure, tissue-specific gene expression, chromosomal localization, and lung in situ hybridization
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DOI：
10.1165/ajrcmb.17.4.2826
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发表时间：
1997-10-01
影响因子：
6.4
通讯作者：
Crapo, JD
中科院分区：
文献类型：
--
作者：
Folz, RJ;Guan, JZ;Crapo, JD
细胞外超氧化物歧化酶(EC-SOD)是主要的胞外抗氧化酶。通过对互补DNA克隆的鉴定和纯化蛋白的氨基酸序列分析，确定了小鼠EC-SOD的一级结构。序列分析表明，小鼠EC-SOD是由251个氨基酸组成的前体蛋白，预测其相对分子质量为27,400 D。对纯化的小鼠肺EC-SOD的氨基酸末端微序列分析表明，该序列以SSFDLADRLDPV-开头，表明最初合成的EC-SOD含有一个24个氨基酸的前体多肽，成熟蛋白全长227个氨基酸。预测共翻译信号肽酶最有可能切割位点的计算机算法表明，加工将发生在氨基酸18和19或20和21之间，这意味着EC-SOD最初可能是以前体蛋白的形式合成的。和人的EC-SOD一样，成熟的小鼠EC-SOD也是糖基化的。小鼠EC-SOD全长1,834个碱基对，与大鼠EC-SOD的同源性为82%(蛋白质含量为79%)，与人EC-SOD的同源性仅为60%(蛋白质含量为60%)。通过种间回交单倍型分析，小鼠EC-SOD基因座(Sod3)位于小鼠5号染色体上Qdpr基因座的远端0.9+/-0.9厘米器官，这表明EC-SOD的人类同源基因将定位于人类QDPR基因座(4p15.3)附近。在Northern印迹分析的9个组织中，肾脏和肺是目前为止表达EC-SOD信使RNA的主要组织。通过在小鼠肺组织中的原位杂交，我们证明EC-SOD基因在肺泡II型上皮细胞中高度定位表达。这些数据表明，肺泡型IT细胞在调节EC-SOD在肺中的抗氧化功能中发挥着核心作用。
Extracellular superoxide dismutase (EC-SOD) is the major extracellular antioxidant enzyme. We have determined the primary structure of mouse EC-SOD by characterization of complementary DNA (cDNA) clones and by amino-acid sequence analysis of purified protein. cDNA sequence analysis indicates that mouse EC-SOD is synthesized as a 251-amino-acid precursor protein with a predicted molecular weight of 27,400 D. Amino-terminal micro sequence analysis of purified mature mouse lung EC-SOD demonstrated the sequence to begin with SSFDLADRLDPV-, These results indicate that EC-SOD as initially synthesized contains a 24-amino-acid precursor peptide, and that the mature protein is 227 amino acids in length. Computer algorithms that predict the most Likely site of cotranslational signal peptidase cleavage suggest that processing will occur between amino acids 18 and 19 or 20 and 21, which implies that EC-SOD may be initially synthesized as a pre-pro-protein. Like human EC-SOD, mature mouse EC-SOD is glycosylated. The full-length mouse EC-SOD cDNA is 1,834 base pairs long and is 82% (79% for protein) identical to rat EC-SOD, but only 60% (60% for protein) identical to human EC-SOD. The mouse EC-SOD gene locus (Sod3) was mapped by interspecific backcross haplotype analysis as being 0.9 +/- 0.9 centimorgans distal to the Qdpr locus on mouse Chromosome 5, a position suggesting that the human homologue of EC-SOD will map close to the human QDPR locus (4p15.3). Of nine tissues examined by Northern blot analysis, those of the kidney and lung are by far the major tissues that express EC-SOD messenger RNA. Using in situ hybridization in the mouse lung, we demonstrate EC-SOD gene expression to be highly localized to alveolar Type II epithelial cells. These data suggest that alveolar Type IT cells play a central role in mediating EC-SOD antioxidant function in the lung.