The caveolin-binding motif of the pathogen-related yeast protein Pry1, a member of the CAP protein superfamily, is required for in vivo export of cholesteryl acetate
The caveolin-binding motif of the pathogen-related yeast protein Pry1, a member of the CAP protein superfamily, is required for in vivo export of cholesteryl acetate
复制标题
DOI：
10.1194/jlr.m047126
复制
发表时间：
2014-05-01
影响因子：
6.5
通讯作者：
Schneiter, Roger
中科院分区：
文献类型：
--
作者：
Choudhary, Vineet;Darwiche, Rabih;Schneiter, Roger
属于 CAP 超家族的蛋白质存在于生命的各个领域，并参与不同的生理过程。然而，人们对它们的分子作用模式知之甚少。酿酒酵母表达该超家族的三个成员：病原体相关酵母 (Pry)1、-2 和 -3。我们最近表明，Pry 功能是胆固醇乙酸酯分泌所必需的，并且 Pry 蛋白结合胆固醇和胆固醇乙酸酯，这表明 CAP 超家族成员通常可能起到结合甾醇或相关小疏水化合物的作用。在这里，我们分析了 Pry1 与甾醇结合的模式。计算模型表明，配体结合可以通过相对保守性较差的柔性环的置换来发生，在一些 CAP 家族成员中，该环与小窝蛋白结合基序表现出同源性。该基序内的点突变消除了胆固醇乙酸酯的输出，但不影响胆固醇的结合。位于小窝蛋白结合基序外部的残基突变或高度保守的推定催化残基的突变对胆固醇乙酸酯的输出或脂质结合没有影响。这些结果表明，Pry1 以及其他 CAP 家族成员的小窝蛋白结合基序对于选择性脂质结合至关重要，并且脂质结合可能通过包含该基序的环的置换而发生。
Proteins belonging to the CAP superfamily are present in all kingdoms of life and have been implicated in different physiological processes. Their molecular mode of action, however, is poorly understood. Saccharomyces cerevisiae expresses three members of this superfamily, pathogen-related yeast (Pry)1, -2, and -3. We have recently shown that Pry function is required for the secretion of cholesteryl acetate and that Pry proteins bind cholesterol and cholesteryl acetate, suggesting that CAP superfamily members may generally act to bind sterols or related small hydrophobic compounds. Here, we analyzed the mode of sterol binding by Pry1. Computational modeling indicates that ligand binding could occur through displacement of a relatively poorly conserved flexible loop, which in some CAP family members displays homology to the caveolin-binding motif. Point mutations within this motif abrogated export of cholesteryl acetate but did not affect binding of cholesterol. Mutations of residues located outside the caveolin-binding motif, or mutations in highly conserved putative catalytic residues had no effect on export of cholesteryl acetate or on lipid binding. These results indicate that the caveolin-binding motif of Pry1, and possibly of other CAP family members, is crucial for selective lipid binding and that lipid binding may occur through displacement of the loop containing this motif.