Essential role of the A'α/Aβ gap in the N-terminal upstream of LOV2 for the blue light signaling from LOV2 to kinase in Arabidopsis photototropin1, a plant blue light receptor.
Essential role of the A'α/Aβ gap in the N-terminal upstream of LOV2 for the blue light signaling from LOV2 to kinase in Arabidopsis photototropin1, a plant blue light receptor.
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DOI：
10.1371/journal.pone.0124284
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发表时间：
2015
期刊：
影响因子：
3.7
通讯作者：
Tokutomi S
中科院分区：
文献类型：
--
作者：
Kashojiya S;Okajima K;Shimada T;Tokutomi S
趋光素（Phototropin, phot）是植物体内的一种蓝光受体，参与植物的向光性、叶绿体运动、气孔打开等过程。光分子在其n端有两个光接受结构域LOV (Light-Oxygen-Voltage) 1和2，在其c端有一个丝氨酸/苏氨酸激酶（STK）。STK活性主要受LOV2调控，LOV2具有循环光反应，包括瞬时形成黄素单核苷酸(FMN)-半胱氨酸加合物（S390）。BL信号从LOV2传播到STK的关键事件之一是位于LOV2 c端下游的j α-螺旋的构象变化。相比之下，我们关注的是位于LOV2 n端上游并与j α-螺旋相互作用的A′α-螺旋的作用。利用拟南芥（Arabidopsis thaliana phot1）的LOV2-STK多肽，研究人员发现，截断A′α-螺旋以及在LOV2的A′α和A′β链间隙（A′α/A′β间隙）的Glu474和Lys475处的氨基酸替换（A′α/A′β间隙）会破坏bl1诱导的STK活化，但不会影响S390的形成。胰蛋白酶以光依赖的方式消化了Lys603和Lys475处的LOV2-STK，这表明bl诱导了j α-螺旋和间隙的结构变化。Lys603的消化速度比Lys475快。以Glu474Ala和Lys475Ala为替代物，可以观察到BL诱导的结构变化，说明BL信号到达了j α-螺旋和A′α/Aβ间隙，但不能激活STK，间隙中的氨基酸残基Glu474和Lys475在高等植物中是保守的，可能是连接j α-螺旋结构变化和STK激活的连接点。
Phototropin (phot) is a blue light (BL) receptor in plants and is involved in phototropism, chloroplast movement, stomata opening, etc. A phot molecule has two photo-receptive domains named LOV (Light-Oxygen-Voltage) 1 and 2 in its N-terminal region and a serine/threonine kinase (STK) in its C-terminal region. STK activity is regulated mainly by LOV2, which has a cyclic photoreaction, including the transient formation of a flavin mononucleotide (FMN)-cysteinyl adduct (S390). One of the key events for the propagation of the BL signal from LOV2 to STK is conformational changes in a Jα-helix residing downstream of the LOV2 C-terminus. In contrast, we focused on the role of the A’α-helix, which is located upstream of the LOV2 N-terminus and interacts with the Jα-helix. Using LOV2-STK polypeptides from Arabidopsis thaliana phot1, we found that truncation of the A’α-helix and amino acid substitutions at Glu474 and Lys475 in the gap between the A’α and the Aβ strand of LOV2 (A’α/Aβ gap) to Ala impaired the BL-induced activation of the STK, although they did not affect S390 formation. Trypsin digested the LOV2-STK at Lys603 and Lys475 in a light-dependent manner indicating BL-induced structural changes in both the Jα-helix and the gap. The digestion at Lys603 is faster than at Lys475. These BL-induced structural changes were observed with the Glu474Ala and the Lys475Ala substitutes, indicating that the BL signal reached the Jα-helix as well as the A’α/Aβ gap but could not activate STK. The amino acid residues, Glu474 and Lys475, in the gap are conserved among the phots of higher plants and may act as a joint to connect the structural changes in the Jα-helix with the activation of STK.
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