Structure of porcine pancreatic phospholipase A2 at 2.6 A resolution and comparison with bovine phospholipase A2.
Structure of porcine pancreatic phospholipase A2 at 2.6 A resolution and comparison with bovine phospholipase A2.
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DOI：
10.1016/s0022-2836(83)80328-3
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发表时间：
1983-07
影响因子：
5.6
通讯作者：
B. Dijkstra;R. Renetseder;K. H. Kalk;W. Hol;J. Drenth
中科院分区：
文献类型：
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作者：
B. Dijkstra;R. Renetseder;K. H. Kalk;W. Hol;J. Drenth
以前发表的猪胰腺磷脂酶原A2的三维结构在3分辨率下被发现与牛磷脂酶A2和牛磷脂酶原A2的结构不相容。这是出乎意料的，因为这些酶的氨基酸序列非常同源。因此，猪酶的晶体结构重新确定使用分子置换方法与牛磷脂酶作为父模型。通过快速傅里叶变换和最小二乘法对晶体结构进行了精细化，其分辨率为2·6，R因子为0·241。晶体中似乎含有磷脂酶A2，而不是磷脂酶A2原。显然，蛋白质在所采用的结晶条件下缓慢转化。我们的研究表明，与以前的报道相比，猪磷脂酶A2的三维结构与牛磷脂酶A2非常相似，包括活性位点。较小的差异，观察到在一些残基参与结合的聚集底物。然而，在环59至70中存在明显的构象差异，其中63位的单个取代（牛瓦尔→猪苯丙氨酸）导致肽链完全重排。除了活性位点中的钙离子外，晶体中还存在第二个钙离子;它位于晶体学2重轴上，稳定了两个相邻分子之间的相互作用。
The previously published three-dimensional structure ofporcinepancreatic prophospholipase A2at 3resolution was found to be incompatible with the structures ofbovinephospholipase A2andbovineprophospholipase A2. This was unexpected because of the very homologous amino acid sequences of these enzymes. Therefore, the crystal structure of the porcine enzyme was redetermined using molecular replacement methods with bovine phospholipase as the parent model. The structure was crystallographically refined at 2·6resolution by fast Fourier transform and restrained least-squares procedures to anR-factor of 0·241.The crystals appeared to contain phospholipase A2and not prophospholipase A2. Apparently the protein is slowly converted under the crystallization conditions employed. Our investigation shows that, in contrast to the previous report, the three-dimensional structure of porcine phospholipase A2is very similar to that of bovine phospholipase A2, including the active site. Smaller differences were observed in some residues involved in the binding of aggregated substrates. However, an appreciable conformational difference is in the loop 59 to 70, where a single substitution at position 63 (bovine Val→porcine Phe) causes a complete rearrangement of the peptide chain.In addition to the calcium ion in the active site, a second calcium ion is present in the crystals; this is located on a crystallographic 2-fold axis and stabilizes the interaction between two neighbouring molecules.