Structural basis for the interaction between pectin methylesterase and a specific inhibitor protein
Structural basis for the interaction between pectin methylesterase and a specific inhibitor protein
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DOI：
10.1105/tpc.104.028886
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发表时间：
2005-03-01
期刊：
影响因子：
11.6
通讯作者：
Tsernoglou, D
中科院分区：
文献类型：
--
作者：
Di Matteo, A;Giovane, A;Tsernoglou, D
果胶是植物细胞壁的主要成分之一，以高度甲酯化的形式分泌，随后在 muro 中被果胶甲酯酶 (PME) 脱酯化。在许多发育过程中，PME 受到差异表达或蛋白质抑制剂 (PME1) 的翻译后控制的调节。 PEl 通常对植物 PME 有活性，但对微生物酶无效。在这里，我们以 1.9 埃的分辨率描述了番茄果实 (Lycopersicon esculentum) 中最丰富的 PME 同种型和猕猴桃 (Actinidia deliciosa) 中的 PMEI 之间复合物的三维结构。该酶折叠成果胶酶典型的右手平行 P 螺旋结构。该抑制剂几乎都是螺旋状的，四个长α螺旋以反平行方式排列在经典的上下四螺旋束中。这两种蛋白质形成化学计量比为 1:1 的复合物，其中抑制剂覆盖了假定活性位点所在的酶的浅裂隙。抑制剂的四螺旋束大致垂直于 PME 平行 P 螺旋的主轴，并且该束的三个螺旋与酶相互作用。相互作用界面显示出极性特征，这是由可溶性蛋白质形成的非专性复合物的典型特征。通过该复合物的结构，可以深入了解抑制剂对植物 PME 的特异性以及这些酶的调节机制。
Pectin, one of the main components of the plant cell wall, is secreted in a highly methyl-esterified form and subsequently deesterified in muro by pectin methylesterases (PMEs). In many developmental processes, PMEs are regulated by either differential expression or posttranslational control by protein inhibitors (PMEls). PMEls are typically active against plant PMEs and ineffective against microbial enzymes. Here, we describe the three-dimensional structure of the complex between the most abundant PME isoform from tomato fruit (Lycopersicon esculentum) and PMEI from kiwi (Actinidia deliciosa) at 1.9-angstrom resolution. The enzyme folds into a right-handed parallel P-helical structure typical of pectic enzymes. The inhibitor is almost all helical, with four long alpha-helices aligned in an antiparallel manner in a classical up-and-down four-helical bundle. The two proteins form a stoichiometric 1:1 complex in which the inhibitor covers the shallow cleft of the enzyme where the putative active site is located. The four-helix bundle of the inhibitor packs roughly perpendicular to the main axis of the parallel P-helix of PME, and three helices of the bundle interact with the enzyme. The interaction interface displays a polar character, typical of nonobligate complexes formed by soluble proteins. The structure of the complex gives an insight into the specificity of the inhibitor toward plant PMEs and the mechanism of regulation of these enzymes.