Department of Human Anatomy and Physiology, Section of Physiology, University of Padova, 35131, Italy.
J Cell Sci. 2010 Oct 1;123(Pt 19):3276-83. doi: 10.1242/jcs.071316. Epub 2010 Sep 7.
An analysis of SNAP-25 isoform sequences indicates that there is a highly conserved arginine residue (198 in vertebrates, 206 in the genus Drosophila) within the C-terminal region, which is cleaved by botulinum neurotoxin A, with consequent blockade of neuroexocytosis. The possibility that it may play an important role in the function of the neuroexocytosis machinery was tested at neuromuscular junctions of Drosophila melanogaster larvae expressing SNAP-25 in which Arg206 had been replaced by alanine. Electrophysiological recordings of spontaneous and evoked neurotransmitter release under different conditions as well as testing for the assembly of the SNARE complex indicate that this residue, which is at the P(1)' position of the botulinum neurotoxin A cleavage site, plays an essential role in neuroexocytosis. Computer graphic modelling suggests that this arginine residue mediates protein-protein contacts within a rosette of SNARE complexes that assembles to mediate the fusion of synaptic vesicles with the presynaptic plasma membrane.
对 SNAP-25 同工型序列的分析表明，在 C 末端区域存在一个高度保守的精氨酸残基（脊椎动物中的 198 位，果蝇属中的 206 位），该残基被肉毒神经毒素 A 切割，导致神经囊泡释放受阻。在表达 SNAP-25 的黑腹果蝇幼虫的神经肌肉接头中，该残基（位于肉毒神经毒素 A 切割位点的 P(1)’位置）可能在神经囊泡释放机制的功能中发挥重要作用，对此进行了测试。在不同条件下，对自发和诱发的神经递质释放进行电生理记录，并对 SNARE 复合物的组装进行测试，结果表明该残基在神经囊泡释放中起关键作用。计算机图形建模表明，该精氨酸残基介导 SNARE 复合物形成的玫瑰花环内的蛋白质-蛋白质接触，这些复合物组装起来介导突触小泡与突触前质膜融合。
