Differences in structure and distribution of the molecular forms of acetylcholinesterase.
Differences in structure and distribution of the molecular forms of acetylcholinesterase.
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乙酰胆碱酯酶的分子形式的结构和分布差异。
DOI：
10.1083/jcb.108.6.2301
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发表时间：
1989-06
期刊：
影响因子：
--
通讯作者：
Taylor P
中科院分区：
文献类型：
--
作者：
Abramson SN;Ellisman MH;Deerinck TJ;Maulet Y;Gentry MK;Doctor BP;Taylor P
在加利福尼亚电鳐的电器官中发现了两种结构不同的乙酰胆碱酯酶分子形式。一种形式是尺寸不对称的，由异源亚基组成。另一种是疏水性的，由同源亚基组成。序列特异性抗体针对合成肽产生，所述合成肽对应于乙酰胆碱酯酶的不对称形式的催化亚基的COOH末端区域（Lys 560-Leu 575）。这些抗体与乙酰胆碱酯酶的不对称形式反应，但不与疏水形式反应。这些结果证实了最近的研究表明，不对称形式的COOH-末端结构域不同于疏水形式，并代表了抗体的选择性的催化亚基的不对称形式的第一个演示。此外，单克隆抗体（4 E7）的反应性表位，以前显示为选择性的疏水形式的乙酰胆碱酯酶，已被确定为N-连接的复合碳水化合物，从而定义两种形式之间的翻译后差异。用这两种形式选择性抗体以及泛选择性多克隆抗体和单克隆抗体，在光镜和电镜下对电鳐电器中两种形式的乙酰胆碱酯酶进行了免疫定位研究。这两种形式几乎完全定位于受神经支配的表面的电细胞。然而，它们沿受神经支配的表面有差异地分布沿着。特定的不对称形式的免疫反应性被限制在突触并置区和突触后膜的内陷，形成突触沟。相反，免疫反应性归因于疏水形式选择性地发现沿着非突触表面的神经末梢，并没有观察到在突触间隙或在内陷的突触后膜。这种差异分布表明，这两种形式的乙酰胆碱酯酶可能发挥不同的作用，在调节局部浓度的乙酰胆碱在突触。
Two structurally distinct molecular forms of acetylcholinesterase are found in the electric organs of Torpedo californica. One form is dimensionally asymmetric and composed of heterologous subunits. The other form is hydrophobic and composed of homologous subunits. Sequence- specific antibodies were raised against a synthetic peptide corresponding to the COOH-terminal region (Lys560-Leu575) of the catalytic subunits of the asymmetric form of acetylcholinesterase. These antibodies reacted with the asymmetric form of acetylcholinesterase, but not with the hydrophobic form. These results confirm recent studies suggesting that the COOH-terminal domain of the asymmetric form differs from that of the hydrophobic form, and represent the first demonstration of antibodies selective for the catalytic subunits of the asymmetric form. In addition, the reactive epitope of a monoclonal antibody (4E7), previously shown to be selective for the hydrophobic form of acetylcholinesterase, has been identified as an N-linked complex carbohydrate, thus defining posttranslational differences between the two forms. These two form- selective antibodies, as well as panselective polyclonal and monoclonal antibodies, were used in light and electron microscopic immunolocalization studies to investigate the distribution of the two forms of acetylcholinesterase in the electric organ of Torpedo. Both forms were localized almost exclusively to the innervated surface of the electrocytes. However, they were differentially distributed along the innervated surface. Specific asymmetric-form immunoreactivity was restricted to areas of synaptic apposition and to the invaginations of the postsynaptic membrane that form the synaptic gutters. In contrast, immunoreactivity attributable to the hydrophobic form was selectively found along the non-synaptic surface of the nerve terminals and was not observed in the synaptic cleft or in the invaginations of the postsynaptic membrane. This differential distribution suggests that the two forms of acetylcholinesterase may play different roles in regulating the local concentration of acetylcholine in the synapse.