Copper(2+) Binding to the Surface Residue Cysteine 111 of His46Arg Human Copper-Zinc Superoxide Dismutase, a Familial Amyotrophic Lateral Sclerosis Mutant

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• 作者：Hongbin Liu ; Haining Zhu ; Daryl K. Eggers ; Aram M. Nersissian ; Kym F. Faull ; Joy J. Goto ; Jingyuan Ai ; Joann Sanders-Loehr ; Edith Butler Gralla ; and Joan Selverstone Valentine
• 刊名：Biochemistry
• 出版年：2000
• 出版时间：July 18, 2000
• 年：2000
• 卷：39
• 期：28
• 页码：8125 - 8132
• 全文大小：143K
• 年卷期：v.39,no.28(July 18, 2000)
• ISSN：1520-4995

文摘

Mutations in copper-zinc superoxide dismutase (CuZnSOD) cause 25% of familial amyotrophiclateral sclerosis (FALS) cases. This paper examines one such mutant, H46R, which has no superoxidedismutase activity yet presumably retains the gain-of-function activity that leads to disease. We demonstratethat Cu²⁺ does not bind to the copper-specific catalytic site of H46R CuZnSOD and that Cu²⁺ competeswith other metals for the zinc binding site. Most importantly, Cu²⁺ was found to bind strongly to a surfaceresidue near the dimer interface of H46R CuZnSOD. Cysteine was identified as the new binding site onthe basis of multiple criteria including UV-vis spectroscopy, RR spectroscopy, and chemical derivatization.Cysteine 111 was pinpointed as the position of the reactive ligand by tryptic digestion of the modifiedprotein and by mutational analysis. This solvent-exposed residue may play a role in the toxicity of thisand other FALS CuZnSOD mutations. Furthermore, we propose that the two cysteine 111 residues, foundon opposing subunits of the same dimeric enzyme, may provide a docking location for initial metal insertionduring biosynthesis of wild-type CuZnSOD in vivo.