Yuan Amelia T, Liu Lijia, Chang Lo-Yueh, Stillman Martin J
Department of Chemistry, University of Western Ontario, 1151 Richmond Street, London, Ontario N6A 5B7 Canada.
National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu 300092, Taiwan, ROC.
Inorg Chem. 2023 Aug 14;62(32):13011-13020. doi: 10.1021/acs.inorgchem.3c01796. Epub 2023 Aug 3.
The field of designing artificial metalloproteins has yet to effectively tackle the incorporation of multimetal clusters, which is a key component of natural metalloproteins, such as metallothioneins (MTs) and calmodulin. MT is a physiological, essential, cysteine-rich metalloprotein that binds to a variety of metals but is only known to form metal-thiolate clusters with Cd, Zn, and Cu. Bismuth is a xenobiotic metal and a component of metallodrugs used to treat gastric ulcers and cancer, as well as an emerging metal used in industrial practices. Electrospray ionization mass spectrometry, UV-visible spectroscopy, and extended X-ray absorption fine structure spectroscopy were used to probe the Bi binding site structures in apo-MT3 (brain-located MT) at pH 7.4 and 2 and provide the complete set of binding affinities. We discovered the highly cooperative formation of a novel Bi species, BiMT3, under physiological conditions, where each Bi ion is coordinated by three cysteinyl thiolates, with one of the thiolates bridging between the two Bi ions. This cluster structure was associated with a strong visible region absorption band, which was disrupted by the addition of Zn and reversibly disrupted by acidification and increased temperature. This is the first reported presence of bridging cysteines for a xenobiotic metal in MT3 and the BiMT structure is the first Bi cluster found in a metalloprotein.
人工金属蛋白的设计领域尚未有效解决多金属簇的整合问题，而多金属簇是天然金属蛋白（如金属硫蛋白（MTs）和钙调蛋白）的关键组成部分。MT是一种生理必需的、富含半胱氨酸的金属蛋白，能与多种金属结合，但目前仅知其能与镉、锌和铜形成金属硫醇盐簇。铋是一种外源金属，是用于治疗胃溃疡和癌症的金属药物的成分，也是工业实践中新兴的金属。采用电喷雾电离质谱、紫外可见光谱和扩展X射线吸收精细结构光谱来探测脱辅基MT3（脑定位MT）在pH 7.4和pH 2条件下的铋结合位点结构，并提供完整的结合亲和力。我们发现在生理条件下一种新型铋物种BiMT3的高度协同形成，其中每个铋离子由三个半胱氨酸硫醇盐配位，其中一个硫醇盐在两个铋离子之间形成桥连。这种簇结构与一个强可见区吸收带相关，添加锌会破坏该吸收带，酸化和温度升高会使其可逆破坏。这是首次报道MT3中外源金属存在桥连半胱氨酸，且BiMT结构是在金属蛋白中发现的首个铋簇。
