LOEX/CUO-recherche, Centre hospitalier affilié universitaire de Québec, Hôpital du Saint-Sacrement, 1050 Chemin Ste-Foy, Québec (Québec), Canada.
Langmuir. 2012 Feb 21;28(7):3516-23. doi: 10.1021/la203896n. Epub 2012 Feb 7.
Lecithin:retinol acyltransferase (LRAT) is a 230 amino acid membrane-associated protein which catalyzes the esterification of all-trans-retinol into all-trans-retinyl ester. A truncated form of LRAT (tLRAT), which contains the residues required for catalysis but which is lacking the N- and C-terminal hydrophobic segments, was produced to study its membrane binding properties. Measurements of the maximum insertion pressure of tLRAT, which is higher than the estimated lateral pressure of membranes, and the positive synergy factor a argue in favor of a strong binding of tLRAT to phospholipid monolayers. Moreover, the binding, secondary structure and orientation of the peptides corresponding to its N- and C-terminal hydrophobic segments of LRAT have been studied by circular dichroism and polarization-modulation infrared reflection absorption spectroscopy in monolayers. The results show that these peptides spontaneously bind to lipid monolayers and adopt an α-helical secondary structure. On the basis of these data, a new membrane topology model of LRAT is proposed where its N- and C-terminal segments allow to anchor this protein to the lipid bilayer.
视黄醇酰基转移酶（LRAT）是一种 230 个氨基酸的膜相关蛋白，它催化全反式视黄醇酯化成全反式视黄醇酯。LRAT 的一种截断形式（tLRAT），其包含催化所需的残基，但缺乏 N 和 C 末端疏水性片段，被产生以研究其膜结合特性。tLRAT 的最大插入压力的测量值高于估计的膜侧向压力，以及正协同因子 a 有利于 tLRAT 与磷脂单层的强结合。此外，通过圆二色性和偏振调制红外反射吸收光谱在单层中研究了与 LRAT 的 N 和 C 末端疏水性片段相对应的肽的结合、二级结构和取向。结果表明，这些肽自发地结合到脂质单层并采用α-螺旋二级结构。基于这些数据，提出了 LRAT 的一种新的膜拓扑模型，其中其 N 和 C 末端片段允许将该蛋白锚定到脂质双层。
