Okada Mariko, Miura Takashi, Nakabayashi Takakazu
Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba-ku, Sendai 980-8578, Japan.
Department of Pharmaceutical Sciences, International University of Health and Welfare, 2600-1 Kitakanemaru, Ohtawara, Tochigi 324-8501, Japan.
J Inorg Biochem. 2017 Apr;169:97-105. doi: 10.1016/j.jinorgbio.2017.01.009. Epub 2017 Jan 22.
The reduction and binding of copper ions to the Cys/Trp motif, which is characterized by two cysteines and two tryptophans, in the extracellular N-terminal domain of the copper transporter (Ctr) protein of fungi are investigated using the model peptides of Ctr4 and Ctr5 from Schizosaccharomyces pombe. The Cys/Trp motif of Ctr5 can reduce Cu(II) and ligate Cu(I), which is the same as that of Ctr4 previously reported. Titration of Cu(II) and Cu(I) ions indicates that both the Cys/Trp motifs of Ctr4 and Ctr5 reduce two Cu(II) and bind two Cu(I) per one peptide. However, the coordination structure of the Cu(I)-peptide complex differs between Ctr4 and Ctr5. Cu(I) is bound to the Cys/Trp motif of Ctr5 via cysteine thiolate-Cu(I) bonds and cation-π interaction with tryptophan, as reported for Ctr4, and a histidine residue in the Cys/Trp motif of Ctr5 is suggested to interact with Cu(I) via its Nτ atom. Ctr4 and Ctr5 exhibit a heterotrimeric form within cell membranes and the copper transport mechanism of the Ctr4/Ctr5 heterotrimer is discussed along with quantitative evaluation of the Cu(I)-binding constant of the Cys/Trp motif.
利用粟酒裂殖酵母中Ctr4和Ctr5的模型肽，研究了铜离子与真菌铜转运蛋白（Ctr）胞外N端结构域中以两个半胱氨酸和两个色氨酸为特征的Cys/Trp基序的还原和结合情况。Ctr5的Cys/Trp基序能够还原Cu（II）并连接Cu（I），这与先前报道的Ctr4相同。Cu（II）和Cu（I）离子滴定表明，Ctr4和Ctr5的Cys/Trp基序均能还原两个Cu（II），且每个肽结合两个Cu（I）。然而，Ctr4和Ctr5的Cu（I）-肽复合物的配位结构有所不同。与Ctr4一样，Cu（I）通过半胱氨酸硫醇盐-Cu（I）键和与色氨酸的阳离子-π相互作用与Ctr5的Cys/Trp基序结合，并且Ctr5 的Cys/Trp基序中的一个组氨酸残基被认为通过其Nτ原子与Cu（I）相互作用。Ctr4和Ctr5在细胞膜内呈现异源三聚体形式，并结合Cys/Trp基序的Cu（I）结合常数的定量评估，讨论了Ctr4/Ctr5异源三聚体的铜转运机制。
