Contribution of human manganese superoxide dismutase tyrosine 34 to structure and catalysis.
Contribution of human manganese superoxide dismutase tyrosine 34 to structure and catalysis.
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DOI：
10.1021/bi8023288
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发表时间：
2009-04-21
期刊：
影响因子：
2.9
通讯作者：
Silverman, David N.
中科院分区：
文献类型：
--
作者：
Perry, J. Jefferson P.;Hearn, Amy S.;Cabelli, Diane E.;Nick, Harry S.;Tainer, John A.;Silverman, David N.
超氧化物歧化酶(SOD)在控制与衰老、癌症和神经退行性疾病有关的活性氧(ROS)水平方面至关重要。呼吸过程中产生的超氧化物歧化酶(O2·−)由SOD2基因产物--同源四聚体锰超氧化物歧化酶(MnSOD2)清除。在这里，我们研究了高度保守的活性位点残基Tyr34的结构和催化作用，基于该位点突变的MnSOD酶的结构和功能研究。用5种不同的氨基酸取代Tyr34，保留了活性中心蛋白质的结构和组装，但使超氧化物还原的催化速率常数显著降低。形成产物抑制复合体的速率常数也降低，但幅度小得多，导致突变酶的产物抑制形式净增加。晶体结构和催化速率的比较也表明，一个突变Y34V中断了氢键网络，这与产物抑制复合体的快速解离有关。值得注意的是，在Tyr34突变体中的三个中，我们还观察到了一种催化中间体，这在以前还没有报道过。因此，这些突变体建立了一种捕获催化中间体的方法，有望帮助阐明催化的机制。
Superoxide dismutase (SOD) enzymes are critical in controlling levels of reactive oxygen species (ROS) that are linked to aging, cancer and neurodegenerative disease. Superoxide (O2 •−) produced during respiration is removed by the product of the SOD2 gene, the homotetrameric manganese superoxide dismutase (MnSOD). Here, we examine the structural and catalytic roles of the highly conserved active-site residue Tyr34, based upon structure-function studies of MnSOD enzymes with mutations at this site. Substitution of Tyr34 with five different amino acids retained the active site protein structure and assembly, but causes a substantial decrease in the catalytic rate constant for the reduction of superoxide. The rate constant for formation of product inhibition complex also decreases but to a much lesser extent, resulting in a net increase in the product inhibition form of the mutant enzymes. Comparisons of crystal structures and catalytic rates also suggest that one mutation, Y34V, interrupts the hydrogen-bonded network, which is associated with a rapid dissociation of the product-inhibited complex. Notably, with three of the Tyr34 mutants we also observe an intermediate in catalysis, which has not been reported previously. Thus, these mutants establish a means to trap a catalytic intermediate that promises to help elucidate the mechanism of catalysis.
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影响因子：
64.5
作者：
BORGSTAHL, GEO;PARGE, HE;TAINER, JA
通讯作者：
TAINER, JA
影响因子：
2.9
作者：
Cabelli, DE;Guan, Y;Silverman, DN
通讯作者：
Silverman, DN
影响因子：
2.9
作者：
Greenleaf, WB;Jefferson, J;Silverman, DN
通讯作者：
Silverman, DN
DOI：
10.1107/s0907444998003254
发表时间：
1998-09-01
期刊：
ACTA CRYSTALLOGRAPHICA SECTION D-BIOLOGICAL CRYSTALLOGRAPHY
影响因子：
--
作者：
Brunger, AT;Adams, PD;Warren, GL
通讯作者：
Warren, GL
影响因子：
2.9
作者：
Barondeau, DP;Kassmann, CJ;Getzoff, ED
通讯作者：
Getzoff, ED