Reid Korey M, Sunanda Punnepalli, Raghothama S, Krishnan V V
Department of Chemistry, California State University, Fresno, California, 93740.
NMR Research Centre, Indian Institute of Science, Bangalore, 560012, India.
Biopolymers. 2017 Nov;108(6). doi: 10.1002/bip.23036. Epub 2017 Jul 22.
Intrinsically disordered proteins (IDP) lack a well-defined 3D-structure under physiological conditions, yet, the inherent disorder represented by an ensemble of conformation plays a critical role in many cellular and regulatory processes. Nucleoporins, or Nups, are the proteins found in the nuclear pore complex (NPC). The central pore of the NPC is occupied by Nups, which have phenylalanine-glycine domain repeats and are intrinsically disordered, and therefore are termed FG-Nups. These FG-domain repeats exhibit differing cohesiveness character and differ from least (FG) to most (GLFG) cohesive. The designed FG-Nup is a 25 AA model peptide containing a noncohesive FG-motif flanked by two cohesive GLFG-motifs (WT peptide). Complete NMR-based ensemble characterization of this peptide along with a control peptide with an F>A substitution (MU peptide) are discussed. Ensemble characterization of the NMR-determined models suggests that both the peptides do not have consistent secondary structures and continue to be disordered. Nonetheless, the role of cohesive elements mediated by the GLFG motifs is evident in the WT ensemble of structures that are more compact than the MU peptide. The approach presented here allows an alternate way to investigate the specific roles of distinct amino acid motifs that translate into the long-range organization of the ensemble of structures and in general on the nature of IDPs.
内在无序蛋白（IDP）在生理条件下缺乏明确的三维结构，然而，由一系列构象所代表的内在无序在许多细胞和调节过程中起着关键作用。核孔蛋白，即核孔复合体（NPC）中的蛋白质。NPC的中央孔被核孔蛋白占据，这些核孔蛋白具有苯丙氨酸-甘氨酸结构域重复序列且内在无序，因此被称为FG-核孔蛋白。这些FG结构域重复序列表现出不同的内聚性特征，从最弱（FG）到最强（GLFG）内聚性各不相同。设计的FG-核孔蛋白是一种25个氨基酸的模型肽，包含一个非内聚性的FG基序，两侧是两个内聚性的GLFG基序（野生型肽）。本文讨论了该肽以及一个具有F>A替换的对照肽（MU肽）基于核磁共振的完整系综表征。核磁共振确定模型的系综表征表明，这两种肽都没有一致的二级结构，并且仍然是无序的。尽管如此，由GLFG基序介导的内聚元件的作用在比MU肽更紧凑的野生型结构系综中是明显的。这里介绍的方法提供了一种替代途径，用于研究不同氨基酸基序的特定作用，这些作用转化为结构系综的远程组织，以及一般而言内在无序蛋白的性质。
