Harel M, Kryger G, Rosenberry T L, Mallender W D, Lewis T, Fletcher R J, Guss J M, Silman I, Sussman J L
Department of Structural Biology, Weizmann Institute of Science, Rehovot, Israel.
Protein Sci. 2000 Jun;9(6):1063-72. doi: 10.1110/ps.9.6.1063.
We have crystallized Drosophila melanogaster acetylcholinesterase and solved the structure of the native enzyme and of its complexes with two potent reversible inhibitors, 1,2,3,4-tetrahydro-N-(phenylmethyl)-9-acridinamine and 1,2,3,4-tetrahydro-N-(3-iodophenyl-methyl)-9-acridinamine--all three at 2.7 A resolution. The refined structure of D. melanogaster acetylcholinesterase is similar to that of vertebrate acetylcholinesterases, for example, human, mouse, and fish, in its overall fold, charge distribution, and deep active-site gorge, but some of the surface loops deviate by up to 8 A from their position in the vertebrate structures, and the C-terminal helix is shifted substantially. The active-site gorge of the insect enzyme is significantly narrower than that of Torpedo californica AChE, and its trajectory is shifted several angstroms. The volume of the lower part of the gorge of the insect enzyme is approximately 50% of that of the vertebrate enzyme. Upon binding of either of the two inhibitors, nine aromatic side chains within the active-site gorge change their conformation so as to interact with the inhibitors. Some differences in activity and specificity between the insect and vertebrate enzymes can be explained by comparison of their three-dimensional structures.
我们已使黑腹果蝇乙酰胆碱酯酶结晶，并解析了天然酶及其与两种强效可逆抑制剂（1,2,3,4-四氢-N-(苯甲基)-9-吖啶胺和1,2,3,4-四氢-N-(3-碘苯甲基)-9-吖啶胺）形成的复合物的结构，所有这三种结构的分辨率均为2.7埃。黑腹果蝇乙酰胆碱酯酶的精细结构在整体折叠、电荷分布和深邃的活性位点峡谷方面与脊椎动物的乙酰胆碱酯酶（如人类、小鼠和鱼类的乙酰胆碱酯酶）相似，但一些表面环与其在脊椎动物结构中的位置偏差高达8埃，且C末端螺旋发生了显著移位。昆虫酶的活性位点峡谷比加州电鳐乙酰胆碱酯酶的活性位点峡谷明显更窄，其轨迹也偏移了几埃。昆虫酶峡谷下部的体积约为脊椎动物酶的50%。在结合两种抑制剂中的任何一种后，活性位点峡谷内的九个芳香族侧链会改变其构象以与抑制剂相互作用。通过比较昆虫和脊椎动物酶的三维结构，可以解释它们在活性和特异性方面的一些差异。
