Machado Benelli Elaine, Buck Martin, Polikarpov Igor, Maltempi de Souza Emanuel, Cruz Leonardo M, Pedrosa Fábio O
Department of Biochemistry, Universidade Federal do Paraná, C. Postal 19046, Curitiba, Brazil.
Eur J Biochem. 2002 Jul;269(13):3296-303. doi: 10.1046/j.1432-1033.2002.03011.x.
PII-like proteins are signal transduction proteins found in bacteria, archaea and eukaryotes. They mediate a variety of cellular responses. A second PII-like protein, called GlnK, has been found in several organisms. In the diazotroph Herbaspirillum seropedicae, PII protein is involved in sensing nitrogen levels and controlling nitrogen fixation genes. In this work, the crystal structure of the unliganded H. seropedicae PII was solved by X-ray diffraction. H. seropedicae PII has a Gly residue, Gly108 preceding Pro109 and the main-chain forms a beta turn. The glycine at position 108 allows a bend in the C-terminal main-chain, thereby modifying the surface of the cleft between monomers and potentially changing function. The structure suggests that the C-terminal region of PII proteins may be involved in specificity of function, and nonenteric diazotrophs are found to have the C-terminal consensus XGXDAX(107-112). We are also proposing binding sites for ATP and 2-oxoglutarate based on the structural alignment of PII with PII-ATP/GlnK-ATP, 5-carboxymethyl-2-hydroxymuconate isomerase and 4-oxalocrotonate tautomerase bound to the inhibitor 2-oxo-3-pentynoate.
类PII蛋白是在细菌、古菌和真核生物中发现的信号转导蛋白。它们介导多种细胞反应。在几种生物中发现了第二种类PII蛋白，称为GlnK。在固氮菌草螺菌中，PII蛋白参与感知氮水平并控制固氮基因。在这项工作中，通过X射线衍射解析了未结合配体的草螺菌PII的晶体结构。草螺菌PII在Pro109之前有一个Gly残基Gly108，主链形成一个β转角。108位的甘氨酸使C末端主链发生弯曲，从而改变单体之间裂隙的表面并可能改变功能。该结构表明，PII蛋白的C末端区域可能参与功能特异性，并且发现非肠道固氮菌具有C末端共有序列XGXDAX(107 - 112)。基于PII与结合抑制剂2-氧代-3-戊炔酸的PII-ATP/GlnK-ATP、5-羧甲基-2-羟基粘康酸异构酶和4-草酰巴豆酸互变异构酶的结构比对，我们还提出了ATP和2-氧代戊二酸的结合位点。
