Bajjalieh S M, Peterson K, Linial M, Scheller R H
Howard Hughes Medical Institute, Stanford University, CA 94305-5426.
Proc Natl Acad Sci U S A. 1993 Mar 15;90(6):2150-4. doi: 10.1073/pnas.90.6.2150.
Molecular cloning of a cDNA encoding synaptic vesicle protein 2 (SV2) revealed that it is homologous to a family of proton cotransporters from bacteria and fungi and to a related family of glucose transporters found in mammals. The similarity to proton cotransporters raised the possibility that SV2 might mediate the uptake of neurotransmitters into vesicles, an activity known to require a proton gradient. To determine whether SV2 is a member of a family of vesicular proteins, we used the SV2 clone to screen for similar cDNAs in rat brain. We characterized 42 clones, 25 of which encode SV2 and 4 of which encode a protein, SV2B, that is 65% identical and 78% similar to SV2. The protein encoded by SV2B cDNA is recognized by the monoclonal antibody that defines the SV2 protein. When SV2B is expressed in COS cells, antibody labeling is reticular in nature, suggesting that SV2B, like SV2 (hence, SV2A), is segregated to intracellular membranes. The expression of SV2B is limited to neural tissue. While both forms of SV2 are expressed in all brain regions, SV2B is expressed at highest levels in the cortex and hippocampus, whereas the highest level of expression of SV2A is in subcortical regions. Therefore, the SV2 proteins, like other characterized synaptic vesicle proteins, comprise a small gene family.
编码突触小泡蛋白2（SV2）的cDNA的分子克隆显示，它与细菌和真菌中的质子共转运蛋白家族以及哺乳动物中发现的相关葡萄糖转运蛋白家族同源。与质子共转运蛋白的相似性增加了SV2可能介导神经递质摄取到小泡中的可能性，已知该活性需要质子梯度。为了确定SV2是否是小泡蛋白家族的成员，我们使用SV2克隆在大鼠脑中筛选相似的cDNA。我们鉴定了42个克隆，其中25个编码SV2，4个编码一种蛋白质SV2B，它与SV2的同一性为65%，相似性为78%。SV2B cDNA编码的蛋白质被定义SV2蛋白的单克隆抗体识别。当SV2B在COS细胞中表达时，抗体标记本质上是网状的，这表明SV2B与SV2（因此，SV2A）一样，定位于细胞内膜。SV2B的表达仅限于神经组织。虽然两种形式的SV2在所有脑区均有表达，但SV2B在皮层和海马中的表达水平最高，而SV2A的最高表达水平在皮层下区域。因此，SV2蛋白与其他已鉴定的突触小泡蛋白一样，构成一个小基因家族。
