Five coplanar anion binding sites on one face of phospholipase A2.: Relationship to interface binding
Five coplanar anion binding sites on one face of phospholipase A2.: Relationship to interface binding
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DOI：
10.1021/bi002514g
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发表时间：
2001-01-23
期刊：
影响因子：
2.9
通讯作者：
Bahnson, BJ
中科院分区：
文献类型：
--
作者：
Pan, YH;Epstein, TM;Bahnson, BJ
我们报道了猪胰IB磷脂酶A（2）（PLA 2）与五个硫酸根或磷酸根阴离子结合的晶体学二聚体的结构。在每个结构中，一分子四面体模拟物MJ 33 [1-十六烷基-3-（三氟乙基）-sn-甘油基-2-磷酸甲醇]和五种阴离子在二聚体的两个亚基之间共享。MJ 33的sn-2-磷酸结合在一个亚基（A）的活性位点中，烷基链穿过亚基-亚基界面延伸到第二个亚基（B）的活性位点槽中。这两个亚基被堆积在一起，它们之间沿着埋着一个大的疏水和去溶剂化的表面，五个阴离子定义了一个平面。阴离子通过与每个亚基的两个阳离子残基（R6和K10）直接接触以及通过与其他可极化配体的近距离氢键相互作用而结合。“二聚体”的这些特征表明PLA 2与阴离子界面处的阴离子基团的结合可以由通过H-键合的配位主导，仅需要部分电荷补偿。值得注意的是，由接触表面限定的平面类似于酶的i面[Ramirez，F.，和Jain，M. K. 03 The Dog of the Woman（1991）功能：Genet. 9，229-239]，其已经被提出与基底界面接触用于界面催化转换。此外，这些结构不仅提供了一个视图的活性PLA 2复合到阴离子界面，但也提供了洞察环境的四面体中间体的限速化学步骤的周转周期。两者合计，我们的研究结果提供了一个原子分辨率的结构视图的活性形式的PLA 2与阴离子界面的i面相互作用。
We report the structures of the crystallographic dimer of porcine pancreatic IB phospholipase A(2) (PLA2) with either five sulfate or phosphate anions bound. In each structure, one molecule of a tetrahedral mimic MJ33 [1-hexadecyl-3-(trifluoroethyl)-sn-glycero-2-phosphomethanol] and the five anions are shared between the two subunits of the dimer, The sn-2-phosphate of MJ33 is bound in the active site of one subunit (A), and the alkyl chain extends into the active site slot of the second subunit (B) across the subunit-subunit interface. The two subunits are packed together with a large hydrophobic and desolvated surface buried between them along with the five anions that define a plane. The anions bind by direct contact with two cationic residues (R6 and K10) per subunit and through closer-range H-bonding interactions with other polarizable ligands. These features of the "dimer" suggest that the binding of PLA2 to the anionic groups at the anionic interface may be dominated by coordination through H-bonding with only a partial charge compensation needed. Remarkably, the plane defined by the contact surface is similar to the i-face of the enzyme [Ramirez, F., and Jain, M. K. (1991) Proteins: Struct., Funct., Genet. 9, 229-239], which has been proposed to make contact with the substrate interface for the interfacial catalytic turnover. Additionally, these structures not only offer a view of the active PLA2 complexed to an anionic interface but also provide insight into the environment of the tetrahedral intermediate in the rate-limiting chemical step of the turnover cycle. Taken together, our results offer an atomic-resolution structural view of the i-face interactions of the active form of PLA2 associated to an anionic interface.