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The synaptic vesicle protein SV 31 assembles into a dimer and transports Zn 2+
Author(s) -
Waberer Lisa,
Henrich Erik,
Peetz Oliver,
Morgner Nina,
Dötsch Volker,
Bernhard Frank,
Volknandt Walter
Publication year - 2017
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/jnc.13886
Subject(s) - histidine , chemistry , biophysics , synaptic vesicle , vesicle , divalent , aspartic acid , biochemistry , lysine , binding site , dimer , stereochemistry , amino acid , biology , membrane , organic chemistry
The integral synaptic vesicle protein SV 31 has been shown to bind divalent cations. Here, we demonstrate that SV 31 protein synthesized within a cell‐free system binds Zn 2+ and to a lower extent Ni 2+ and Cu 2+ ions. Expression with Zn 2+ stabilized the protein and increased solubility. SV 31 was preferentially monomeric in detergent and revealed specific binding of Zn 2+ . When co‐translationally inserted into defined nanodisc bilayers, SV 31 assembled into dimeric complexes, resulting in increased binding of Zn 2+ . Putative Zn 2+ ‐binding motifs within SV 31 comprise aspartic acid and histidine residues. Site‐directed mutagenesis of two conserved aspartic acid residues leads to a potent decrease in Zn 2+ binding but did not affect dimerization. Chemical modification of histidine residues abolished some of the Zn 2+ ‐binding capacity. We demonstrate proton‐dependent transport of Zn 2+ as by accumulation of fluorescent FluoZin‐1 inside of SV 31‐containing proteoliposomes. Transport activity has a K m value of 44.3 μM and required external Zn 2+ and internal acidic pH . Our results demonstrate that the synaptic vesicle‐integral protein SV 31 functions as a proton‐dependent Zn 2+ transporter. SV 31 may attribute specific and yet undiscovered functions to subsets of synapses.