The Effect of Protein Electrostatic Interactions on Globular Protein-Polymer Block Copolymer Self-Assembly
The Effect of Protein Electrostatic Interactions on Globular Protein-Polymer Block Copolymer Self-Assembly
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DOI：
10.1021/acs.biomac.6b00522
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发表时间：
2016-09-01
影响因子：
6.2
通讯作者：
Olsen, Bradley D.
中科院分区：
文献类型：
--
作者：
Lam, Christopher N.;Yao, Helen;Olsen, Bradley D.
超折叠绿色荧光蛋白（GFP）的突变用于设计具有0、-8和-21的形式净电荷的GFP变体，提供一组三种蛋白质，其中总电荷变化以调节蛋白质蛋白质相互作用，同时控制蛋白质大小和三级结构。在将聚（N-异丙基丙烯酰胺）（PNIPAM）与这三种GFP变体中的每一种缀合后，使用小角X射线散射（SAXS）、去偏振光散射（DPLS）和比浊法的组合来表征它们的形态，研究了这三种嵌段共聚物的浓溶液相行为。超荷GFP之间的静电排斥抑制有序化，增加有序-无序转变浓度（C-ODT）并降低有序纳米结构的质量，如通过初级散射峰的半峰全宽所测量的。相比之下，中性带电的GFP的电荷分布导致其最大的偶极矩，计算约蛋白质的质心，在三个GFP变体和自我互补的Janus样静电表面电位，增强纳米结构的形成。不同的静电性质导致不同的蛋白质蛋白质相互作用，影响高温形态，包括形成宏观相分离或均匀的胶束相和较小的六边形有序窗口的增压GFP。GFP（-21）-PNIPAM的有序纳米结构的质量的小的改进可以通过蛋白质-二价阳离子相互作用来实现。因此，不同的蛋白质电荷和静电被证明是一种调节蛋白质-蛋白质相互作用的大小和方向性以控制自组装的方法。
Mutation of a superfolder green fluorescent protein (GFP) was used to design GFP variants with formal net charges of 0, -8, and -21, providing a set of three proteins in which the total charge is varied to tune protein protein interactions while controlling for the protein size and tertiary structure. After conjugating poly(N-isopropylacrylamide) (PNIPAM) to each of these three GFP variants, the concentrated solution phase behavior of these three block copolymers is studied using a combination of small-angle X-ray scattering (SAXS), depolarized light scattering (DPLS), and turbidimetry to characterize their morphologies. The electrostatic repulsion between supercharged GFP suppresses ordering, increasing the order-disorder transition concentration (C-ODT) and decreasing the quality of the ordered nanostructures as measured by the full width at half-maximum of the primary scattering peak. By contrast, the charge distribution of the neutrally charged GFP results in its largest dipole moment, calculated about the protein's center of mass, among the three GFP variants and a self-complementary Janus-like electrostatic surface potential that enhances nanostructure formation. The different electrostatic properties result in different protein protein interactions that affect the high temperature morphologies, including the formation of macrophase separated or homogeneous micellar phases and the smaller hexagonal ordering window of the supercharged GFP. Small improvements-in the quality of the ordered nanostructures of GFP(-21)-PNIPAM can be achieved through protein-divalent cation interactions. Therefore, varying protein charge and electrostatics is demonstrated as a method of tuning the magnitude and directionality of protein-protein interactions to control self-assembly.