The synaptic vesicle protein SV31 assembles into a dimer and transports Zn²⁺

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• 作者：Lisa Waberer ; Erik Henrich ; Oliver Peetz ; Nina Morgner ; Volker Dö ; tsch ; Frank Bernhard and Walter Volknandt
• 刊名：Journal of Neurochemistry
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：140
• 期：2
• 页码：280-293
• 全文大小：1925K
• ISSN：1471-4159

文摘

The integral synaptic vesicle protein SV31 has been shown to bind divalent cations. Here, we demonstrate that SV31 protein synthesized within a cell-free system binds Zn²⁺ and to a lower extent Ni²⁺ and Cu²⁺ ions. Expression with Zn²⁺ stabilized the protein and increased solubility. SV31 was preferentially monomeric in detergent and revealed specific binding of Zn²⁺. When co-translationally inserted into defined nanodisc bilayers, SV31 assembled into dimeric complexes, resulting in increased binding of Zn²⁺. Putative Zn²⁺-binding motifs within SV31 comprise aspartic acid and histidine residues. Site-directed mutagenesis of two conserved aspartic acid residues leads to a potent decrease in Zn²⁺ binding but did not affect dimerization. Chemical modification of histidine residues abolished some of the Zn²⁺-binding capacity. We demonstrate proton-dependent transport of Zn²⁺ as by accumulation of fluorescent FluoZin-1 inside of SV31-containing proteoliposomes. Transport activity has a K_m value of 44.3 μM and required external Zn²⁺ and internal acidic pH. Our results demonstrate that the synaptic vesicle-integral protein SV31 functions as a proton-dependent Zn²⁺ transporter. SV31 may attribute specific and yet undiscovered functions to subsets of synapses.