The metal binding properties of the zinc site of yeast copper-zinc superoxide dismutase: implications for amyotrophic lateral sclerosis

被引：0

作者：

T. J. Lyons

A. Nersissian

H. Huang

H. Yeom

C. R. Nishida

J. A. Graden

E. B. Gralla

J. S. Valentine

机构：

[1] Nutritional Sciences Program,

[2] Department of Molecular Biology,undefined

[3] 217 Gwynn Hall,undefined

[4] University of Missouri-Columbia,undefined

[5] Columbia,undefined

[6] MO 65211,undefined

[7] USA,undefined

[8] Department of Chemistry and Biochemistry,undefined

[9] University of California,undefined

[10] Los Angeles,undefined

[11] 607 Circle Drive South,undefined

[12] Box 951569,undefined

[13] Los Angeles,undefined

[14] CA 90095-1569,undefined

[15] USA Tel.: +1-310-8259835 Fax: +1-310-2067197 e-mail: jsc@chem.ucla.edu,undefined

[16] Department of Computer Science,undefined

[17] University of California,undefined

[18] Los Angeles,undefined

[19] 405 Hilgard,undefined

[20] Los Angeles,undefined

[21] CA 90095-1569,undefined

[22] USA,undefined

[23] School of Pharmacy,undefined

[24] University of California,undefined

[25] San Fransisco,undefined

[26] 513 Parnassus Avenue,undefined

[27] Box 0446,undefined

[28] Room S-1134,undefined

[29] San Fransisco,undefined

[30] CA 94143 USA,undefined

[31] Kelly Scientific Resources,undefined

[32] 1710 Walton Road,undefined

[33] Suite 301,undefined

[34] Bluebell,undefined

[35] PA 19420,undefined

[36] USA,undefined

来源：

JBIC Journal of Biological Inorganic Chemistry | 2000年 / 5卷

关键词：

Key words Copper; Zinc; Superoxide dismutase; Amyotrophic lateral sclerosis; Yeast;

D O I：

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摘要：

We have investigated factors that influence the properties of the zinc binding site in yeast copper-zinc superoxide dismutase (CuZnSOD). The properties of yeast CuZnSOD are essentially invariant from pH 5 to pH 9. However, below this pH range there is a change in the nature of the zinc binding site which can be interpreted as either (1) a change in metal binding affinity from strong to weak, (2) the expulsion of the metal bound at this site, or (3) a transition from a normal distorted tetrahedral ligand orientation to a more symmetric arrangement of ligands. This change is strongly reminiscent of a similar pH-induced transition seen for the bovine protein and, based on the data presented herein, is proposed to be a property that is conserved among CuZnSODs. The transition demonstrated for the yeast protein is not only sensitive to the pH of the buffering solution but also to the occupancy and redox status of the adjacent copper binding site. Furthermore, we have investigated the effect of single site mutations on the pH- and redox-sensitivity of Co2+ binding at the zinc site. Each of the mutants H46R, H48Q, H63A, H63E, H80C, G85R, and D83H is capable of binding Co2+ to a zinc site with a distorted tetrahedral geometry similar to that of wild-type. However, they do so only if Cu+ is bound at the copper site or if the pH in raised to near physiological levels, indicating that the change at the zinc binding site seen in the wild-type is conserved in the mutants, albeit with an altered pKa. The mutants H71C and D83A did not bind Co2+ in a wild-type-like fashion under any of the conditions tested. This study reveals that the zinc binding site is exquisitely sensitive to changes in the protein environment. Since three of the mutant yeast proteins investigated here contain mutations analogous to those that cause ALS (amyotrophic lateral sclerosis) in humans, this finding implicates improper metal binding as a mechanism by which CuZnSOD mutants exert their toxic gain of function.

引用

页码：189 / 203

页数：14