Cai Bin, Zheng Qi, Huang Zhong-Xian
Chemical Biology Lab, Department of Chemistry, Fudan University, Shanghai, 200433, China.
Protein J. 2005 Aug;24(6):327-36. doi: 10.1007/s10930-005-7588-0.
Metallothioneins (MTs) are metal-binding proteins with low molecular weight and conservative cysteine residues. Metallothionein-4 (MT-4), one of MT isoforms, is first reported to be distributed in a tissue-specific manner, mainly in stratified squamous epithelia. Here, we compare the properties of metal-thiolate clusters in MT-4 to those in MT-1 and MT-3, including the stabilities toward both pH change and EDTA, as well as the exposure of thiolates to solvent. The metal-thiolate clusters in MT-3 show different property and activity to the reactions compared with MT-4 and MT-1. The structure of metal-thiolate clusters in MT-4 is similar to that of MT-1 from the UV and CD spectra. During pH titration and DTNB reaction, MT-4 and MT-1 exhibit comparable behavior. But while reacting with EDTA, the metal-thiolate clusters in MT-4 are more stable than those of MT-1. We suppose the negative charge of the beta-domain of MT-4 prevents the EDTA attack to MT-4.
金属硫蛋白（MTs）是一类分子量较低且含有保守半胱氨酸残基的金属结合蛋白。金属硫蛋白-4（MT-4）是MT异构体之一，首次被报道以组织特异性方式分布，主要存在于复层鳞状上皮中。在此，我们将MT-4中金属硫醇盐簇的性质与MT-1和MT-3中的进行比较，包括对pH变化和EDTA的稳定性，以及硫醇盐与溶剂的接触情况。与MT-4和MT-1相比，MT-3中的金属硫醇盐簇在反应中表现出不同的性质和活性。从紫外光谱和圆二色光谱来看，MT-4中金属硫醇盐簇的结构与MT-1的相似。在pH滴定和DTNB反应过程中，MT-4和MT-1表现出相似的行为。但在与EDTA反应时，MT-4中的金属硫醇盐簇比MT-1中的更稳定。我们推测MT-4的β结构域的负电荷可防止EDTA对MT-4的攻击。
