Acylation of Lens Proteins

胞浆蛋白的N-酰化是组织中普遍存在的现象，它调节蛋白质的结构和 功能。细胞内的N-酰化类型主要有乙酰化、丙酰化、琥珀酸化和丙二酸化， 它们由乙酰辅酶A、丙酰辅酶A、琥珀酰辅酶A的酶或非酶转移引发 和丙二酰辅酶A分别转化为赖氨酸残基。晶状体蛋白质寿命很长，几乎没有周转，而且 因此，翻译后修饰(PTM)随着年龄的增长而积累。缺乏具有酶活性的蛋白质， 特别是在晶状体的核心，禁止PTM的反转。因此，如果脱脂酶在晶状体中很弱， 酰化主要是一种导致晶状体蛋白质永久性修饰的单向反应，看起来 事实如此(基于我们的初步数据)。酰化作用对晶状体蛋白的影响仍然很大。 未知。我们先前的研究表明，乙酰化使α-晶体蛋白成为更好的伴侣。此外, 我们的初步数据显示，晶状体蛋白也是丙酰化、琥珀酸化和丙二酸化的，而且 乙酰化和琥珀酸化提高了蛋白质的热稳定性和溶解性。因此，我们 假设晶状体蛋白的酰化是一种有益的PTM，有助于维持α的伴侣活性- 晶状体蛋白以及晶状体蛋白在老化过程中的稳定性和溶解性。我们将在以下方面测试这一假设 三个目标。在目标1中，我们将确定人晶状体α中的主要酰化位点？晶体蛋白的质量。 光谱分析并确定年龄对这些修饰的影响。在目标2中，我们将确定 酰化对α-晶体蛋白结构和功能的影响。在目标3中，我们将评估 酰化对晶状体蛋白的稳定性和溶解性的影响，并确定酰化是否可以用于 改善老化的人类晶状体的弹性。

N-acylation of cytosolic proteins is a common occurrence in tissues, and it regulates protein structure and function. The major N-acylation types in cells are acetylation, propionylation, succinylation and malonylation, which are initiated by the enzymatic or non-enzymatic transfer of acetyl CoA, propionyl CoA, succinyl CoA and malonyl CoA to lysine residues, respectively. Lens proteins are long lived with little or no turnover, and thus, post-translational modifications (PTMs) accumulate with age. The lack of enzymatically active proteins, particularly in the core of the lens, prohibits the reversal of PTMs. Thus, if deacylases are weak in the lens, acylation is mostly a one-way reaction that leads to permanent modifications of lens proteins, which appears to be the case (based on our preliminary data). The effects of acylation on lens proteins remain largely unknown. As shown in our previous study, the acetylation makes α-crystallin a better chaperone. In addition, our preliminary data show that lens proteins are also propionylated, succinylated and malonylated and that acetylation and succinylation increase the thermal stability and solubility of the proteins. Thus, we hypothesize that acylation of lens proteins is a beneficial PTM that helps maintain the chaperone activity of α- crystallin as well as the stability and solubility of lens proteins during aging. We will test this hypothesis in three aims. In Aim 1, we will determine the major acylation sites in human lens α-crystallin by mass spectrometric analyses and determine the effect of age on these modifications. In Aim 2, we will determine effects of acylation on the structure and function of α-crystallin. In Aim 3, we will evaluate the effects of acylation on the stability and solubility of lens proteins and determine whether acylation can be used to improve the compromised resilience of aged human lenses.