Ligand-induced formation of transient dimers of mammalian 12/15-lipoxygenase: A key to allosteric behavior of this class of enzymes?
Ligand-induced formation of transient dimers of mammalian 12/15-lipoxygenase: A key to allosteric behavior of this class of enzymes?
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DOI：
10.1002/prot.23227
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发表时间：
2012-03-01
影响因子：
2.9
通讯作者：
Kuehn, Hartmut
中科院分区：
文献类型：
--
作者：
Ivanov, Igor;Shang, Weifeng;Kuehn, Hartmut
哺乳动物脂氧合酶 (LOX) 与细胞防御反应有关，对于生理稳态很重要。自被发现以来，LOX 一直被认为具有表现出变构特性的单体酶的功能。在水溶液中，兔12/15-LOX主要以水合单体形式存在，但局部理化环境的变化表明单体二聚体平衡。由于酶的变构特征很难用单一配体结合位点模型来解释，因此我们提出变构效应子的结合可能会将单体二聚体平衡转向二聚体形成。为了检验这一假设，我们通过小角度 X 射线散射探讨了变构效应子 [13(S)-羟基十八烷-9(Z),11(E)-二烯酸] 对兔 12/15-LOX 结构特性的影响。我们的数据表明，该酶在水溶液中经历配体诱导的二聚化，分子动力学模拟表明，LOX 二聚体在底物脂肪酸存在下可能是稳定的。这些数据为 LOX 二聚体的存在提供了直接的结构证据，其中两个非共价连接的酶分子可能协同工作，因此，这种关联模式可能与 12/15-LOX 的变构特征有关。在单体间界面引入带负电荷的残基（W181E + H585E 和 L183E + L192E）会扰乱野生型 LOX 的疏水二聚体相互作用，这种结构改变可能会导致突变酶的功能扭曲。蛋白质 2011。(c) 2012 Wiley periodicals, Inc.
Mammalian lipoxygenases (LOXs) have been implicated in cellular defense response and are important for physiological homeostasis. Since their discovery, LOXs have been believed to function as monomeric enzymes that exhibit allosteric properties. In aqueous solutions, the rabbit 12/15-LOX is mainly present as hydrated monomer but changes in the local physiochemical environment suggested a monomerdimer equilibrium. Because the allosteric character of the enzyme can hardly be explained using a single ligand binding-site model, we proposed that the binding of allosteric effectors may shift the monomerdimer equilibrium toward dimer formation. To test this hypothesis, we explored the impact of an allosteric effector [13(S)-hydroxyoctadeca-9(Z),11(E)-dienoic acid] on the structural properties of rabbit 12/15-LOX by small-angle X-ray scattering. Our data indicate that the enzyme undergoes ligand-induced dimerization in aqueous solution, and molecular dynamics simulations suggested that LOX dimers may be stable in the presence of substrate fatty acids. These data provide direct structural evidence for the existence of LOX dimers, where two noncovalently linked enzyme molecules might work in unison and, therefore, such mode of association might be related to the allosteric character of 12/15-LOX. Introduction of negatively charged residues (W181E + H585E and L183E + L192E) at the intermonomer interface disturbs the hydrophobic dimer interaction of the wild-type LOX, and this structural alteration may lead to functional distortion of mutant enzymes. Proteins 2011. (c) 2012 Wiley Periodicals, Inc.