Feng Shan, Xu Zhen, Yan Yong-Bin
State Key Laboratory of Biomembrane and Membrane Biotechnology, Department of Biological Sciences and Biotechnology, Tsinghua University, Beijing 100084, China.
J Inorg Biochem. 2008 Apr;102(4):928-35. doi: 10.1016/j.jinorgbio.2007.12.013. Epub 2007 Dec 25.
Creatine kinase (CK) is a key enzyme to maintain the energy homeostasis in vertebrate excitable tissues. Due to its importance in cellular energetics, the activity and level of CK are crucial to cellular and body functions. CK is sensitive to oxidative stresses and is thought to be one of the main targets of oxidative modification in neurodegenerative diseases. In this research, we investigated the effect of copper, an essential trace element for all organisms and an inducer of the reactive oxygen species, on CK refolding. It was found that trace amounts of Cu(2+) (3mol eq of Cu(2+)) could efficiently block the refolding of CK. The Cu(2+)-trapped CK could not be reactivated by the addition of EDTA, but could be reactivated by DTT. Spectroscopic experiments suggested that copper ions blocked CK refolding by specifically binding with the monomeric refolding intermediate, which further retarded CK refolding and promoted the formation of off-pathway aggregates. The results herein suggested that Cu(2+)-induced CK dysfunction might be caused not only by the post-translational oxidation, but also by the direct binding of copper ions with the newly-synthesized polypeptides.
肌酸激酶（CK）是维持脊椎动物可兴奋组织能量稳态的关键酶。由于其在细胞能量代谢中的重要性，CK的活性和水平对细胞及身体功能至关重要。CK对氧化应激敏感，被认为是神经退行性疾病中氧化修饰的主要靶点之一。在本研究中，我们研究了铜（一种所有生物体必需的微量元素且是活性氧的诱导剂）对CK重折叠的影响。结果发现，微量的Cu(2+)（3摩尔当量的Cu(2+)）能够有效阻断CK的重折叠。被Cu(2+)捕获的CK不能通过添加EDTA重新激活，但能被DTT重新激活。光谱实验表明，铜离子通过与单体重折叠中间体特异性结合来阻断CK重折叠，这进一步阻碍了CK重折叠并促进了错误折叠聚集体的形成。本文结果表明，Cu(2+)诱导的CK功能障碍可能不仅是由翻译后氧化引起的，还可能是由铜离子与新合成多肽的直接结合导致的。
