精制的晶体结构unligated adenylosuccinate合成酶从大肠杆菌。
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席尔瓦MM,波兰BW,霍夫曼CR、弗洛姆HJ Honzatko RB
精制的晶体结构unligated adenylosuccinate合成酶从大肠杆菌。
J杂志。1995年12月1日,254(3):431 - 46所示。
- PubMed ID
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7490761 (在PubMed]
- 文摘
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晶体结构的unligated adenylosuccinate合成酶大肠杆菌在空间组织的P2(1)和P2(1) 2(1) 2(1),以r个因子的0.199和0.206对数据2.0和2.5,分别。债券的长度和角度偏离预期值0.011和1.7度的P2(1)晶体形式和0.015和1.7度的P2(1) 2(1) 2(1)晶体形式。多肽链的折叠是由一个中央β褶板,这是由九个平行链和反平行的链十分之一。延长从这个中央β褶板四子域。四子域循环贡献无序的残留物或有很高的热参数。至少三个循环(残留42 52岁,120年到131年和298年到304年)提供必要的残留的假定的合成酶的活性部位。没有配体,合成酶的活性部位存在于一个不明确的构象状态。2、近独立地区贡献残留合成酶的多肽链二聚体之间的界面。一对螺旋(H4和H5)与他们交互symmetry-equivalent配偶的残留不保存在已知序列的合成酶。第二个界面区域涉及守恒的残留属于中央β褶板连接链的结构元素。 Residues putatively involved in the binding of IMP lie at or near the interface between polypeptide chains of the dimer. Of the four sequence elements putatively common to all GTP hydrolases, the synthetase has only the guanine recognition element and a glycine-rich loop (P-loop). Although the base recognition element is essentially identical with those of the p21 ras and G alpha proteins, the P-loop of the synthetase is extended in size relative to the P-loops of other GTP hydrolases. The P-loop has two acid residues (Asp13 and Glu14), which are found in the P-loops of only the synthetase family. Glu14 may be involved in the stabilization of the enlarged P-loop of the synthetase, whereas Asp13 may play a role in catalysis and in the coordination of Mg2+. The structural elements of the p21 ras and G alpha proteins responsible for binding Mg2+ are either absent from the synthetase or unavailable for the coordination of metal cations.