Brouwer M, Brouwer-Hoexum T
Duke University Marine Laboratory, Beaufort, North Carolina 28516.
Arch Biochem Biophys. 1991 Oct;290(1):207-13. doi: 10.1016/0003-9861(91)90610-u.
Organisms have harnessed the unique chemistry of copper for a variety of purposes. However, that same chemistry makes this essential metal toxic at elevated concentrations. Metallothioneins (MTs), a family of small metal-binding proteins, are thought to play a crucial role in the regulation of this reactive ion. Here we report that copper-metallothioneins from the American lobster, Homarus americanus, interact with the tripeptide glutathione (gamma-Glu-Cys-Gly). Glutathione in the cytosolic fraction prepared from the digestive gland of the American lobster coelutes with copper-metallothionein during size-exclusion chromatography. The latter protein can be separated into three isoforms by anion-exchange chromatography. All three isoforms belong to the class I MTs. CuMT-I and -II are very similar, whereas CuMT-III is distinct from isoforms I and II. The interaction between glutathione and MT isoforms was examined by ultrafiltration experiments and size-exclusion HPLC. CuMT-III forms a stable 1:1 complex with glutathione, with a dissociation constant of 1 microM. CuMT-I/II makes a transient complex with glutathione, which releases copper as a copper-glutathione complex. This complex can function as the source of Cu(I) in the restoration of the oxygen-binding capacity of copper-free hemocyanin. These studies suggest that metallothionein and glutathione are intricately linked in the biochemistry of copper regulation.
生物体已利用铜的独特化学性质实现了多种目的。然而，同样的化学性质使得这种必需金属在浓度升高时具有毒性。金属硫蛋白（MTs）是一类小型金属结合蛋白，被认为在这种活性离子的调节中起着关键作用。在此我们报告，美洲龙虾（Homarus americanus）的铜金属硫蛋白与三肽谷胱甘肽（γ-Glu-Cys-Gly）相互作用。在尺寸排阻色谱过程中，从美洲龙虾消化腺制备的胞质组分中的谷胱甘肽与铜金属硫蛋白共洗脱。后者的蛋白质可通过阴离子交换色谱分离为三种同工型。所有三种同工型都属于I类MTs。CuMT-I和-II非常相似，而CuMT-III与同工型I和II不同。通过超滤实验和尺寸排阻高效液相色谱研究了谷胱甘肽与MT同工型之间的相互作用。CuMT-III与谷胱甘肽形成稳定的1:1复合物，解离常数为1 microM。CuMT-I/II与谷胱甘肽形成短暂复合物，该复合物会释放出作为铜-谷胱甘肽复合物的铜。这种复合物可作为无铜血蓝蛋白恢复氧结合能力时Cu(I)的来源。这些研究表明，金属硫蛋白和谷胱甘肽在铜调节的生物化学过程中紧密相连。
