Undetectable intracellular free copper: The requirement of a copper chaperone for superoxide dismutase
Undetectable intracellular free copper: The requirement of a copper chaperone for superoxide dismutase
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DOI：
10.1126/science.284.5415.805
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发表时间：
1999-04-30
期刊：
影响因子：
56.9
通讯作者：
O'Halloran, TV
中科院分区：
文献类型：
--
作者：
Rae, TD;Schmidt, PJ;O'Halloran, TV
超氧化物歧化酶(CCS)基因的顶端伴侣是活性的铜结合形式的超氧化物歧化酶(SOD1)在体内表达所必需的。尽管超氧化物歧化酶对铜(解离常数=6 fM)具有很高的亲和力，而且细胞内SOD1(酵母中为10 mU M)和铜(酵母中为70 mM M)的浓度很高，但体外研究表明，纯化的Cu(I)-YCCS蛋白足以使apo-ySOD1直接激活铜，但只有在严格限制游离铜离子([Cu](Free))的浓度时才是必要的。此外，体内对YCCS的生理需求很容易被高铜浓度和细胞内铜清除系统(如金属硫蛋白)的取消所绕过，这种金属配位蛋白通过直接插入铜辅助因子来激活靶酶，显然具有保护金属离子与细胞内铜清除剂结合的功能。这些结果表明，细胞内[Cu](游离态)被限制在每个细胞内不到一个游离态铜离子的范围内，并表明游离态铜离子池不用于金属酶的生理激活。
The topper chaperone for the superoxide dismutase (CCS) gene is necessary for expression of an active, copper-bound form of superoxide dismutase (SOD1) in vivo in spite of the high affinity of SOD1 for copper (dissociation constant = 6 fM) and the high intracellular concentrations of both SOD1 (10 mu M in yeast) and copper (70 mu M in yeast), In vitro studies demonstrated that purified Cu(I)-yCCS protein is sufficient for direct copper activation of apo-ySOD1 but is necessary only when the concentration of free copper ions ([Cu](free)) is strictly limited. Moreover, the physiological requirement for yCCS in vivo was readily bypassed by elevated copper concentrations and abrogation of intracellular copper-scavenging systems such as the metallothioneins, This metallochaperone protein activates the target enzyme through direct insertion of the copper cofactor and apparently functions to protect the metal ion from binding to intracellular copper scavengers. These results indicate that intracellular [Cu](free) is Limited to less than one free copper ion per cell and suggest that a pool of free copper ions is not used in physiological activation of metalloenzymes.