Sekar K, Biswas R, Li Y, Tsai M, Sundaralingam M
Biological Macromolecular Structure Center, Department of Chemistry, Ohio State Biochemistry Program, 012 Rightmire Hall, 1060 Carmack Road, The Ohio State University, Columbus, OH 43210, USA.
Acta Crystallogr D Biol Crystallogr. 1999 Feb;55(Pt 2):443-7. doi: 10.1107/s0907444998013699.
Crystal structures of the active-site mutants D99A and H48Q and the calcium-loop mutant D49E of bovine phospholipase A2 have been determined at around 1.9 A resolution. The D99A mutant is isomorphous to the orthorhombic recombinant enzyme, space group P212121. The H48Q and the calcium-loop mutant D49E are isomorphous to the trigonal recombinant enzyme, space group P3121. The two active-site mutants show no major structural perturbations. The structural water is absent in D99A and, therefore, the hydrogen-bonding scheme is changed. In H48Q, the catalytic water is present and hydrogen bonded to Gln48 N, but the second water found in native His48 is absent. In the calcium-loop mutant D49E, the two water molecules forming the pentagonal bipyramid around calcium are absent and only one O atom of the Glu49 carboxylate group is coordinated to calcium, resulting in only four ligands.
已在约1.9埃分辨率下测定了牛磷脂酶A2的活性位点突变体D99A和H48Q以及钙环突变体D49E的晶体结构。D99A突变体与正交重组酶同晶型，空间群为P212121。H48Q和钙环突变体D49E与三角重组酶同晶型，空间群为P3121。两个活性位点突变体未显示出主要的结构扰动。D99A中没有结构水，因此氢键模式发生了变化。在H48Q中，催化水存在并与Gln48 N形成氢键，但天然His48中发现的第二个水不存在。在钙环突变体D49E中，围绕钙形成五角双锥的两个水分子不存在，只有Glu49羧酸盐基团的一个O原子与钙配位，导致只有四个配体。
