Sbia M, Diebler M F, Morel N, Israël M
Département de Neurochimie, CNRS, Gif sur Yvette, France.
J Neurochem. 1992 Oct;59(4):1273-9. doi: 10.1111/j.1471-4159.1992.tb08437.x.
The mediatophore is a presynaptic membrane protein that has been shown to translocate acetylcholine (ACh) under calcium stimulation when reconstituted into artificial membranes. The mediatophore subunit, a 15-kDa proteolipid, presents a very high sequence homology with the N,N'-dicyclohexylcarbodiimide (DCCD)-binding proteolipid subunit of the vacuolar-type H(+)-ATPase. This prompted us to study the effect of DCCD, a potent blocker of proton translocation, on calcium-dependent ACh release. The present work shows that DCCD has no effect on ACh translocation either from Torpedo synaptosomes or from proteoliposomes reconstituted with purified mediatophore. However, using [14C]DCCD, we were able to demonstrate that the drug does bind to the 15-kDa proteolipid subunit of the mediatophore. These results suggest that although the 15-kDa proteolipid subunits of the mediatophore and the vacuolar H(+)-ATPase may be identical, different domains of these proteins are involved in proton translocation and calcium-dependent ACh release and that the two proteins have a different membrane organization.
介质载体是一种突触前膜蛋白，当重组到人工膜中时，已显示在钙刺激下能转运乙酰胆碱（ACh）。介质载体亚基是一种15 kDa的蛋白脂质，与液泡型H(+) - ATP酶的N,N'-二环己基碳二亚胺（DCCD）结合蛋白脂质亚基具有非常高的序列同源性。这促使我们研究质子转运的强效阻滞剂DCCD对钙依赖性ACh释放的影响。目前的研究表明，DCCD对来自电鳐突触小体或用纯化的介质载体重组的蛋白脂质体中的ACh转运没有影响。然而，使用[14C]DCCD，我们能够证明该药物确实与介质载体的15 kDa蛋白脂质亚基结合。这些结果表明，尽管介质载体和液泡H(+) - ATP酶的15 kDa蛋白脂质亚基可能相同，但这些蛋白质的不同结构域参与质子转运和钙依赖性ACh释放，并且这两种蛋白质具有不同的膜组织。
