Del Giudice Alessandra, Pavel Nicolae Viorel, Galantini Luciano, Falini Giuseppe, Trost Paolo, Fermani Simona, Sparla Francesca
Department of Chemistry, University of Rome `Sapienza', Rome, Italy.
Department of Chemistry `G. Ciamician', University of Bologna, Bologna, Italy.
Acta Crystallogr D Biol Crystallogr. 2015 Dec 1;71(Pt 12):2372-85. doi: 10.1107/S1399004715018520. Epub 2015 Nov 26.
Oxygenic photosynthetic organisms produce sugars through the Calvin-Benson cycle, a metabolism that is tightly linked to the light reactions of photosynthesis and is regulated by different mechanisms, including the formation of protein complexes. Two enzymes of the cycle, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and phosphoribulokinase (PRK), form a supramolecular complex with the regulatory protein CP12 with the formula (GAPDH-CP122-PRK)2, in which both enzyme activities are transiently inhibited during the night. Small-angle X-ray scattering analysis performed on both the GAPDH-CP12-PRK complex and its components, GAPDH-CP12 and PRK, from Arabidopsis thaliana showed that (i) PRK has an elongated, bent and screwed shape, (ii) the oxidized N-terminal region of CP12 that is not embedded in the GAPDH-CP12 complex prefers a compact conformation and (iii) the interaction of PRK with the N-terminal region of CP12 favours the approach of two GAPDH tetramers. The interaction between the GAPDH tetramers may contribute to the overall stabilization of the GAPDH-CP12-PRK complex, the structure of which is presented here for the first time.
产氧光合生物通过卡尔文-本森循环产生糖类，这一新陈代谢过程与光合作用的光反应紧密相连，并受包括蛋白质复合物形成在内的不同机制调控。该循环中的两种酶，即甘油醛-3-磷酸脱氢酶（GAPDH）和磷酸核酮糖激酶（PRK），与调节蛋白CP12形成一种超分子复合物，其分子式为(GAPDH-CP12₂-PRK)₂，其中两种酶的活性在夜间会被短暂抑制。对来自拟南芥的GAPDH-CP12-PRK复合物及其组分GAPDH-CP12和PRK进行的小角X射线散射分析表明：（i）PRK呈细长、弯曲且扭曲的形状；（ii）未嵌入GAPDH-CP12复合物的CP12氧化N端区域倾向于紧密构象；（iii）PRK与CP12的N端区域相互作用有利于两个GAPDH四聚体靠近。GAPDH四聚体之间的相互作用可能有助于GAPDH-CP12-PRK复合物的整体稳定，本文首次展示了该复合物的结构。
