MacCormack Tyson J, Rundle Amanda M, Malek Michael, Raveendran Abhilash, Meli Maria-Victoria
Department of Chemistry and Biochemistry, Mount Allison University, Sackville, NB, Canada.
PLoS One. 2017 Aug 17;12(8):e0183274. doi: 10.1371/journal.pone.0183274. eCollection 2017.
Engineered nanomaterials can alter the structure and/or function of biological membranes and membrane proteins but the underlying mechanisms remain unclear. We addressed this using a Langmuir phospholipid monolayer containing an active transmembrane protein, glucose-6-phosphatase (G6Pase). Gold nanoparticles (nAu) with varying ligand shell composition and hydrophobicity were synthesized, and their partitioning in the membrane and effects on protein activity characterized. nAu incorporation did not alter the macroscopic properties of the membrane. Atomic force microscopy showed that when co-spread with other components prior to membrane compression, nAu preferentially interacted with G6Pase and each other in a functional group-dependent manner. Under these conditions, all nAu formulations reduced G6Pase aggregation in the membrane, enhancing catalytic activity 5-6 fold. When injected into the subphase beneath pre-compressed monolayers, nAu did not affect G6Pase activity over 60 minutes, implying they were unable to interact with the protein under these conditions. A small but significant quenching of tryptophan fluorescence showed that nAu interacted with G6Pase in aqueous suspension. nAu also significantly reduced the hydrodynamic diameter of G6Pase in aqueous suspension and promoted catalytic activity, likely via a similar mechanism to that observed in co-spread monolayers. Overall, our results show that nAu can incorporate into membranes and associate preferentially with membrane proteins under certain conditions and that partitioning is dependent upon ligand shell chemistry and composition. Once incorporated, nAu can alter the distribution of membrane proteins and indirectly affect their function by improving active site accessibility, or potentially by changing their native structure and distribution in the membrane.
工程纳米材料可以改变生物膜和膜蛋白的结构和/或功能，但其潜在机制仍不清楚。我们使用含有活性跨膜蛋白葡萄糖-6-磷酸酶（G6Pase）的朗缪尔磷脂单层来解决这个问题。合成了具有不同配体壳组成和疏水性的金纳米颗粒（nAu），并表征了它们在膜中的分配情况及其对蛋白质活性的影响。nAu的掺入并未改变膜的宏观性质。原子力显微镜显示，在膜压缩之前与其他成分共铺展时，nAu以官能团依赖的方式优先与G6Pase相互作用并彼此相互作用。在这些条件下，所有nAu制剂均减少了膜中G6Pase的聚集，将催化活性提高了5至6倍。当注入预压缩单层下方的亚相中时，nAu在60分钟内未影响G6Pase活性，这意味着它们在这些条件下无法与蛋白质相互作用。色氨酸荧光的微小但显著的猝灭表明nAu在水悬浮液中与G6Pase相互作用。nAu还显著降低了水悬浮液中G6Pase的流体动力学直径并促进了催化活性，可能是通过与在共铺展单层中观察到的类似机制。总体而言，我们的结果表明，nAu可以在某些条件下掺入膜中并优先与膜蛋白结合，并且分配取决于配体壳的化学性质和组成。一旦掺入，nAu可以改变膜蛋白的分布，并通过改善活性位点的可及性间接影响其功能，或者潜在地通过改变它们在膜中的天然结构和分布来实现。
