Demers Éric, Boisselier Élodie, Horchani Habib, Blaudez Daniel, Calvez Philippe, Cantin Line, Belley Nicolas, Champagne Sophie, Desbat Bernard, Salesse Christian
†CUO-Recherche, Hôpital du Saint-Sacrement, Centre de recherche du CHU de Québec and Département d'ophtalmologie, Faculté de médecine, and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, Canada.
‡CBMN-UMR 5248 CNRS, Université de Bordeaux, IPB, Allée Geoffroy Saint Hilaire, 33600 Pessac, France.
Biochemistry. 2015 Apr 28;54(16):2560-70. doi: 10.1021/bi501517r. Epub 2015 Apr 15.
Retinitis pigmentosa 2 (RP2) is an ubiquitary protein of 350 residues. The N-terminus of RP2 contains putative sites of myristoylation and palmitoylation. The dually acylated protein is predominantly localized to the plasma membrane. However, clinically occurring substitution mutations of RP2 in photoreceptors lead to the expression of a nonacylated protein, which was shown to be misrouted to intracellular organelles using different cell lines. However, the parameters responsible for the modulation of the membrane binding of nonacylated RP2 (naRP2) are still largely unknown. The maximal insertion pressure of naRP2 has thus been determined after its injection into the subphase underneath monolayers of phospholipids, which are typical of photoreceptor membranes. These data demonstrated that naRP2 shows a preferential binding to saturated phospholipid monolayers. Moreover, polarization modulation infrared reflection absorption spectroscopy has allowed comparison of the secondary structure of this protein in solution and upon binding to phospholipid monolayers. In addition, simulations of these spectra have allowed to determine that the β-helix of naRP2 has an orientation of 60° with respect to the normal, which remains unchanged regardless of the type of phospholipid. Finally, ellipsometric measurements of naRP2 demonstrated that its particular affinity for saturated phospholipids can be explained by its larger extent of insertion in this phospholipid monolayer compared to that in polyunsaturated phospholipid monolayers.
视网膜色素变性2（RP2）是一种由350个氨基酸残基组成的普遍存在的蛋白质。RP2的N端含有豆蔻酰化和棕榈酰化的假定位点。这种双重酰化的蛋白质主要定位于质膜。然而，光感受器中临床上出现的RP2替代突变会导致非酰化蛋白的表达，在不同细胞系中，该非酰化蛋白被证明会错误地定位于细胞内细胞器。然而，负责调节非酰化RP2（naRP2）膜结合的参数在很大程度上仍然未知。因此，在将naRP2注入磷脂单层下方的亚相中后，测定了其最大插入压力，磷脂单层是光感受器膜的典型特征。这些数据表明，naRP2对饱和磷脂单层具有优先结合性。此外，偏振调制红外反射吸收光谱法能够比较该蛋白在溶液中以及与磷脂单层结合时的二级结构。此外，对这些光谱的模拟能够确定，naRP2的β螺旋相对于法线的取向为60°，无论磷脂类型如何，该取向均保持不变。最后，对naRP2的椭偏测量表明，其对饱和磷脂的特殊亲和力可以通过其在这种磷脂单层中的插入程度大于在多不饱和磷脂单层中的插入程度来解释。
