Sekar K, Gayathri D, Velmurugan D, Jeyakanthan J, Yamane T, Poi M J, Tsai M D
Bioinformatics Centre, Indian Institute of Science, Bangalore 560 012, India.
Acta Crystallogr D Biol Crystallogr. 2006 Apr;62(Pt 4):392-7. doi: 10.1107/S0907444906001612. Epub 2006 Mar 18.
The lipolytic enzyme phospholipase A2 plays a crucial role in lipid metabolism and catalyzes hydrolysis of the fatty-acid ester bond at the sn-2 position of phospholipids. Here, the crystal structure (1.7 A resolution) of the triple mutant (K53,56,121M) of bovine pancreatic phospholipase A2 complexed with an organic molecule, p-methoxybenzoic acid (anisic acid), is reported. Residues 60-70 (the surface-loop residues) are ordered and adopt conformations which are different from those normally found in structures in which a second calcium ion is present. It is interesting to note that for the first time a third calcium ion has been identified. In addition, four Tris (2-amino-2-hydroxymethyl-1,3-propanediol) molecules were located. It is believed that one of the Tris molecules plays a role in clamping the third calcium ion and that another is involved in controlling the dynamics of the surface loop through hydrogen bonds.
脂解酶磷脂酶A2在脂质代谢中起关键作用，催化磷脂sn-2位脂肪酸酯键的水解。本文报道了牛胰磷脂酶A2的三重突变体（K53、56、121M）与有机分子对甲氧基苯甲酸（茴香酸）复合的晶体结构（分辨率为1.7埃）。60-70位残基（表面环残基）有序排列，其构象与通常在存在第二个钙离子的结构中发现的构象不同。有趣的是，首次鉴定出第三个钙离子。此外，还定位了四个三（2-氨基-2-羟甲基-1,3-丙二醇）分子。据信，其中一个三分子在夹住第三个钙离子方面起作用，另一个通过氢键参与控制表面环的动力学。
