Identification of an amino acid residue in ATP-binding cassette transport G1 critical for mediating cholesterol efflux
Identification of an amino acid residue in ATP-binding cassette transport G1 critical for mediating cholesterol efflux
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DOI：
10.1016/j.bbalip.2011.07.012
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发表时间：
2012-03-01
影响因子：
4.8
通讯作者：
Zhang, Da-wei
中科院分区：
文献类型：
--
作者：
Gao, Xia;Gu, Hongmei;Zhang, Da-wei
ATP结合盒转运体G1（ABCG 1）介导游离胆固醇流出到脂化载脂蛋白A-I（apoA-I）上，并在巨噬细胞胆固醇逆向转运中起重要作用，从而减少动脉粥样硬化。然而，ABCG 1如何介导胆固醇流出到脂化apoA-I上尚不清楚。由于ABCG家族的晶体结构不可用，其他方法如定点突变已被广泛用于鉴定对蛋白质功能重要的氨基酸残基。我们注意到ABCG 1在其假定的跨膜结构域中含有单个半胱氨酸残基。该半胱氨酸残基位于第三推定跨膜结构域内的位置514（Cys（514）），并且是高度保守的。用Ala（C514 A）替换Cys（514）基本上消除了ABCG 1介导的胆固醇流出到脂化的apoA-I上。用更保守的氨基酸残基取代Cys 514。SET或Thr也显著降低胆固醇流出。然而，突变C514 A对蛋白质稳定性和运输没有可检测的影响。突变C514 A也不影响ABCG 1的二聚化。我们的研究结果表明，巯基Cys残基位于位置514起着至关重要的作用，在ABCG 1介导的胆固醇流出。这篇文章是特刊的一部分，题为高密度脂蛋白形成和代谢的进展：向约翰F。Oram（1945-2010）。(C)2011 Elsevier B. V.保留所有权利。
The ATP-binding cassette transporter G1 (ABCG1) mediates free cholesterol efflux onto lipidated apolipoprotein A-I (apoA-I) and plays an important role in macrophage reverse cholesterol transport thereby reducing atherosclerosis. However, how ABCG1 mediates the efflux of cholesterol onto lipidated apoA-I is unclear. Since the crystal structure of ABCG family is not available, other approaches such as site-directed mutagenesis have been widely used to identify amino acid residues important for protein functions. We noticed that ABCG1 contains a single cysteine residue in its putative transmembrane domains. This cysteine residue locates at position 514 (Cys(514)) within the third putative transmembrane domain and is highly conserved. Replacement of Cys(514) with Ala (C514A) essentially abolished ABCG1-mediated cholesterol efflux onto lipidated apoA-I. Substitution of Cys514 with more conserved amino acid residues. Set or Thr, also significantly decreased cholesterol efflux. However, mutation C514A had no detectable effect on protein stability and trafficking. Mutation C514A also did not affect the dimerization of ABCG1. Our findings demonstrated that the sulffiydryl group of Cys residue located at position 514 plays a critical role in ABCG1-mediated cholesterol efflux. This article is part of a Special Issue entitled Advances in High Density Lipoprotein Formation and Metabolism: A Tribute to John F. Oram (1945-2010). (C) 2011 Elsevier B.V. All rights reserved.