Shirvan A, Laskar O, Steiner-Mordoch S, Schuldiner S
Alexander Silberman Institute of Life Sciences, Hebrew University, Jerusalem, Israel.
FEBS Lett. 1994 Dec 12;356(1):145-50. doi: 10.1016/0014-5793(94)01252-0.
Vesicular monoamine transporters (VMAT) catalyze transport of serotonin, dopamine, epinephrine and norepinephrine into subcellular storage organelles in a variety of cells. Accumulation of the neurotransmitter depends on the proton electrochemical gradient across the organelle membrane and involves VMAT-mediated exchange of two lumenal protons with one cytoplasmic amine. It has been suggested in the past that His residues play a role in H+ movement or in its coupling to active transport in H(+)-symporters and antiporters. Indeed VMAT-mediated transport is inhibited by reagents specific for His residues. We have identified one His residue in VMAT1 from rat which is conserved in other vesicular neurotransmitter transporters. Mutagenesis of this His (H419) to either Arg or Cys completely inhibits [3H]serotonin and [3H]dopamine accumulation. Mutagenesis also inhibits other H(+)-dependent partial reactions of VMAT such as the acceleration of binding of the high affinity ligand reserpine, but does not inhibit the [3H]reserpine binding which is not dependent on H+ translocation. It is concluded that His-419 plays a role in energy coupling in r-VMAT1.
囊泡单胺转运体（VMAT）催化5-羟色胺、多巴胺、肾上腺素和去甲肾上腺素转运至多种细胞的亚细胞储存细胞器中。神经递质的积累取决于跨细胞器膜的质子电化学梯度，且涉及VMAT介导的两个管腔质子与一个胞质胺的交换。过去有人提出，组氨酸残基在H⁺ 运动或其与H⁺ 同向转运体和反向转运体中主动转运的偶联中发挥作用。实际上，VMAT介导的转运受到针对组氨酸残基的试剂的抑制。我们在大鼠的VMAT1中鉴定出一个组氨酸残基，该残基在其他囊泡神经递质转运体中保守。将这个组氨酸（H419）突变为精氨酸或半胱氨酸会完全抑制[³H]5-羟色胺和[³H]多巴胺的积累。诱变还会抑制VMAT的其他H⁺ 依赖性部分反应，如高亲和力配体利血平结合的加速，但不抑制不依赖于H⁺ 转运的[³H]利血平结合。得出的结论是，His-419在r-VMAT1的能量偶联中发挥作用。
