The role of protein acetylation in the regulation of photosynthetic light reactions.

为了防止光系统的光抑制和光损伤，光合电子传递必须根据环境条件进行动态调节。在植物适应过程中，蛋白质的几种化学修饰在调节光合产量中起着重要作用。除了磷酸化之外，蛋白质中氨基的乙酰化是所有生物体中主要的翻译后修饰，在参与光合作用的蛋白质中尤其丰富。n端乙酰转移酶或赖氨酸乙酰转移酶催化乙酰基从乙酰辅酶A转移到目标氨基。与n端乙酰化相反，赖氨酸残基（KAc）的乙酰化是可逆的，因此赖氨酸去乙酰化酶负责从蛋白质中去除乙酰基。最近，我们在拟南芥叶绿体中发现了8个新的双特异性乙酰转移酶（GNTAs）。对GNAT2的首次表征表明，这种酶在光合状态转变中是必不可少的。此外，与WT相比，突变体在高光强下表现出更多的能量依赖性猝灭。虽然已经确定了GNAT2的第一个蛋白质底物，但蛋白质乙酰化在光合光反应驯化响应中的具体作用仍未在机制水平上得到理解。该项目将为乙酰化对选定靶蛋白的功能提供新的生化见解，以及密切相关的拟南芥质体乙酰转移酶GNAT1-3参与调节参与能量依赖性猝灭的光合蛋白的蛋白质乙酰化（参见图形摘要P9）。最新的凝胶化学交联技术将用于研究类囊体蛋白复合物组成的差异，这些差异依赖于光和基因型，并将与电子冷冻断层扫描相结合进行3D构建。具体而言，我们将重点关注乙酰化在光合适应响应光有效性变化中的作用。该项目将实现GoPMF目标4，并为GoPMF目标1、2和3做出贡献。

The photosynthetic electron transport has to be dynamically regulated in dependence on environmental conditions to prevent photoinhibition and photodamage of the photosystems. Several chemical modifications of proteins are known to play important roles in modulating photosynthetic yield during plant acclimation responses. Next to phosphorylation, the acetylation of amino groups within proteins is a major posttranslational modification in all organisms and is particularly abundant on proteins involved in photosynthesis. N-terminal acetyltransferases or lysine acetyltransferases catalyze the transfer of the acetyl group from acetyl coenzyme A to the targeted amino group. In contrast to N-terminal acetylation, the acetylation of lysine residues (KAc) is reversible, whereby lysine deacetylases are responsible for the removal of acetyl groups from proteins. Recently, we identified eight new dual-specific acetyltransferases (GNTAs) in chloroplasts of Arabidopsis. The first characterization of GNAT2 revealed that this enzyme is indispensable for photosynthetic state transitions. In addition, the mutants show increased energy-dependent quenching at high light intensities compared to WT. While the first protein substrates of GNAT2 have been identified, the specific role of protein acetylation in the acclimation responses of the photosynthetic light reactions is still not understood on a mechanistic level. This project will provide novel biochemical insights into the functions of acetylation on selected target proteins, as well as the involvement of the closely related Arabidopsis plastidial acetyltransferases GNAT1-3 in regulating protein acetylation of photosynthetic proteins involved in energy-dependent quenching (see also Graphical Abstract P9). Latest in gel chemical crosslinking techniques will be used to study differences in thylakoid protein complex composition in dependence on light and genotype, which will be combined with electron cryotomography for 3D constructions. Specifically, we will focus on the role of acetylation in the photosynthetic acclimation responses to changes in light availability. This project will deliver on Aim 4 of GoPMF and contribute to GoPMF Aims 1, 2 and 3.