Crystal structure of human group X secreted phospholipase A2 -: Electrostatically neutral interfacial binding surface targets zwitterionic membranes
Crystal structure of human group X secreted phospholipase A2 -: Electrostatically neutral interfacial binding surface targets zwitterionic membranes
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DOI：
10.1074/jbc.m202531200
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发表时间：
2002-08-09
影响因子：
4.8
通讯作者：
Bahnson, BJ
中科院分区：
文献类型：
--
作者：
Pan, YH;Yu, BZ;Bahnson, BJ
人类X组（hGX）分泌型磷脂酶A（2）（sPLA（2））的晶体结构已被解析至1.97埃的分辨率。正如预期的那样，蛋白质折叠与先前报道的sPLA（2）结构相似。活性位点结构（包括催化残基的位置以及Ca 2+辅因子周围的第一和第二壳水）高度保守，并且与IB组和IIA组酶显着相似。在（1-12）-N-末端螺旋和C末端的结构中观察到差异。提出这些区域与基底膜表面相互作用。hGX中活性位点槽的开口比人类IIA组sPLA中的大得多（2）。此外，hGX界面结合表面的静电表面电位与人类IIA族sPLA（2）的静电表面电位不同;前者是高度中性的，而后者是高度阳离子的。IB和IIA族酶的这一面上的阳离子残基与膜结合和k*（cat）变构有关。相比之下，当作用于磷脂囊泡或短链磷脂胶束时，hGX不会被脂质界面的阴离子电荷激活。总之，hGX的晶体结构和动力学结果支持这样的结论，即它是作为积极的两性离子阴离子界面，因此，它被预测为目标的两性离子膜表面的哺乳动物细胞。
The crystal structure of human group X (hGX) secreted phospholippse A(2) (sPLA(2)) has been solved to a resolution of 1.97 Angstrom. As expected the protein fold is similar to previously reported sPLA(2) structures. The active site architecture, including the positions of the catalytic residues and the first and second shell water around the Ca2+ cofactor, are highly conserved and remarkably similar to the group IB and group IIA enzymes. Differences are seen in the structures following the (1-12)-N-terminal helix and at the C terminus. These regions are proposed to interact with the substrate membrane surface. The opening to the active site slot is considerably larger in hGX than in human group IIA sPLA(2). Furthermore, the electrostatic surface potential of the hGX interfacial-binding surface does not resemble that of the human group IIA sPLA(2); the former is highly neutral, whereas the latter is highly cationic. The cationic residues on this face of group IB and IIA enzymes have been implicated in membrane binding and in k*(cat) allostery. In contrast, hGX does not show activation by the anionic charge at the lipid interface when acting on phospholipid vesicles or short-chain phospholipid micelles. Together, the crystal structure and kinetic results of hGX supports the conclusion that it is as active onzwitterionic as on anionic interfaces, and thus it is predicted to target the zwitterionic membrane surfaces of mammalian cells.