α-晶体蛋白(αABc)是由αA-晶体蛋白(αAc)和αB-晶体蛋白(αBc)组成的主要蛋白质,在人眼镜片中发现,并通过防止蛋白质聚集和提供耐受压力而作为分子伴侣。然而,随着年龄和白内障的形成,眼晶状体细胞质中αABc的浓度降低,膜结合的αABc相应增加。本研究使用电子顺磁共振(EPR)自旋标记方法来研究胆固醇(Chol)和Chol双层域(CBD)在αAc结合中的作用,αBc,和αABc到人晶状体-脂质(Chol/MHLL)膜的Chol/模型。αAc占据膜表面的最大百分比(MMSO),αBc,和αABc到Chol/MHLL膜在混合比为0时遵循以下趋势:MMSO(αAc)>MMSO(αBc)≈MMSO(αABc),表明与αBc和αABc相比,更大量的αAc与这些膜结合。然而,随着Chol/MHLL膜中Chol浓度的增加,由αAc的MMSO,αBc,和αABc下降,直到它在1.5的混合比下完全减少。αAc的Ka,αBc,和αABc对Chol/MHLL膜的混合比为0时遵循以下趋势:Ka(αBc)≈Ka(αABc)>Ka(αAc),但在Chol/MHLL混合比为1.5时,结合减少,接近于零。随着αAc的增加,膜头基区域附近的迁移率降低,αBc,和αABc结合,Chol拮抗了αAc的能力,αBc,和αABc降低头群区域附近的迁移率。头组区域附近的膜顺序没有观察到明显的变化,随着αAc的增加,αBc,和αABc浓度。我们的结果表明,αAc,αBc,和αABc在0和0.5的混合比下与Chol/MHLL膜结合不同,降低了迁移率并增加了膜头基区域附近的疏水性,可能形成极性和离子分子通过的疏水屏障,包括抗氧化剂(谷胱甘肽),在镜片内部创造氧化环境,导致白内障的发展。然而,所有结合在1.5的混合比下完全减弱,表明高Chol和CBD抑制αAc的结合,αBc,和αABc到膜上,防止疏水屏障的形成,并可能防止白内障形成。
α-Crystallin (αABc) is a major protein comprised of αA-crystallin (αAc) and αB-crystallin (αBc) that is found in the human eye lens and works as a molecular chaperone by preventing the aggregation of proteins and providing tolerance to stress. However, with age and cataract formation, the concentration of αABc in the eye lens cytoplasm decreases, with a corresponding increase in the membrane-bound αABc. This study uses the electron paramagnetic resonance (EPR) spin-labeling method to investigate the role of cholesterol (Chol) and Chol bilayer domains (CBDs) in the binding of αAc, αBc, and αABc to the Chol/model of human lens-lipid (Chol/MHLL) membranes. The maximum percentage of membrane surface occupied (MMSO) by αAc, αBc, and αABc to Chol/MHLL membranes at a mixing ratio of 0 followed the trends: MMSO (αAc) > MMSO (αBc) ≈ MMSO (αABc), indicating that a higher amount of αAc binds to these membranes compared to αBc and αABc. However, with an increase in the Chol concentration in the Chol/MHLL membranes, the MMSO by αAc, αBc, and αABc decreases until it is completely diminished at a mixing ratio of 1.5. The Ka of αAc, αBc, and αABc to Chol/MHLL membranes at a mixing ratio of 0 followed the trend: Ka (αBc) ≈ Ka (αABc) > Ka (αAc), but it was close to zero with the diminished binding at a Chol/MHLL mixing ratio of 1.5. The mobility near the membrane headgroup regions decreased with αAc, αBc, and αABc binding, and the Chol antagonized the capacity of the αAc, αBc, and αABc to decrease mobility near the headgroup regions. No significant change in membrane order near the headgroup regions was observed, with an increase in αAc, αBc, and αABc concentrations. Our results show that αAc, αBc, and αABc bind differently with Chol/MHLL membranes at mixing ratios of 0 and 0.5, decreasing the mobility and increasing hydrophobicity near the membrane headgroup region, likely forming the hydrophobic barrier for the passage of polar and ionic molecules, including antioxidants (glutathione), creating an oxidative environment inside the lens, leading to the development of cataracts. However, all binding was completely diminished at a mixing ratio of 1.5, indicating that high Chol and CBDs inhibit the binding of αAc, αBc, and αABc to membranes, preventing the formation of hydrophobic barriers and likely protecting against cataract formation.