Structure and Function of Mutant SOD1 Derived from 2 bp Deletion in the Gene

肌萎缩侧索硬化症（amyotrophiclateralsclerosis，ALS）是一种皮质、脑干和脊髓运动神经元的退行性疾病。大约10%的ALS是家族性病例，其作为常染色体显性遗传性状遗传。最近的研究表明，大约20%的家族性ALS（FALS）病例具有SOD 1突变，SOD 1是Cu，Zn-超氧化物歧化酶（SOD）的基因，其催化超氧自由基阴离子歧化为过氧化氢和氧分子。所有的FALS突变不改变涉及金属离子配位的任何活性位点残基或形成静电活性通道的残基。相反，大多数的FALS突变位点改变保守的相互作用的亚基折叠和二聚体contact.The突变的SOD与日本的山阴地区发现的北部西部的一部分，从SOD 1的2bp缺失。红细胞、脑组织和淋巴母细胞提取物中的SOD活性显示， ...更多信息 对正常人来说。在大肠杆菌中表达了人SOD 1融合蛋白，并经亲和层析纯化。在融合状态下，SOD活性和蛋白条带清晰可见。但突变SOD 1表达的融合蛋白活性较低，经Xa因子纯化后，融合蛋白的活性和蛋白条带在纯化过程中消失。由于2bp的缺失是非常重要的，通过分析三维模型结构，组成二聚体活性结构，突变SOD的二聚体结构是非常不稳定的，因此从SOD分子中释放的铜离子将是患者组织中氧化应激的来源。尽管SOD突变与FALS的关联机制尚不清楚，但降低的SOD活性可能与FALS无关，但SOD突变体保留了高水平的过氧化活性（功能获得），并利用其自身的歧化产物产生主要种类的羟基自由基，这是氧化应激的来源。少

Amyotrophic lateral sclerosis (ALS) is a degenerative disorder of motor neurons of cortex, brainstem, and spinal cord. About 10% of all ALS are familial cases, which are inherited as an autosomal dominant trait. Recent studies showed that about 20% of familial ALS (FALS) cases have mutations in SOD1, the gene for Cu, Zn-superoxide dismutase (SOD) that catalyzes the dismutation of superoxide radical anions to hydrogen peroxide and oxygen molecules. All of the FALS mutations do not change any active site residues involving the coordination of the metal ions or residues forming the electrostatic active channel. Rather, most of the FALS mutant sites alter conserved interactions critical to the subunit fold and dimer contact.The mutant SOD associated with FALS found in Sanin area north western part of Japan was derived from 2 bp deletion in the SOD1. The SOD activity in extracts from red blood cells, brain tissues, and lymphoblastoid cells revealed an about 50% reduction in FALS patients co … More mpared to normal individuals. The human SOD1 was expressed as a fusion protein in Eschericia coli, then purified by an affinity chromatography. The SOD activity and protein band clearly demonstrated even in the fused states. But, the fused protein expressed from the mutant SOD1 showed clear but very low activity, After the separation of mutant SOD from the fused protein by Factor Xa, the activity and the protein band on the gel disappeared during the purification process. As the 2 bp deletion was found to be very important, by analyzing the three dimensional modeL structure, to compose the dimeric active structure, The dimer structure of the mutant SOD is very labile, thus copper ions released from the SOD molecules will be the source of oxidative stress in tissues of patients. Although the association mechanism of the mutations of SOD with FALS is still unknown, the lowered SOD activity may not be associated FALS but the SOD mutants retain high levels of peroxidative activity (the gain-of-function), and utilize its own dismutation product producing the main species hydroxyl radicals which is the source of oxidative stress. Less