Okumura Masaki, Kanemura Shingo, Matsusaki Motonori, Kinoshita Misaki, Saio Tomohide, Ito Dai, Hirayama Chihiro, Kumeta Hiroyuki, Watabe Mai, Amagai Yuta, Lee Young-Ho, Akiyama Shuji, Inaba Kenji
Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, 6-3 Aramakiaza Aoba, Aoba-ku, Sendai, Miyagi 980-8578, Japan.
Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, 6-3 Aramakiaza Aoba, Aoba-ku, Sendai, Miyagi 980-8578, Japan; School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda, Hyogo 669-1337, Japan.
Structure. 2021 Dec 2;29(12):1357-1370.e6. doi: 10.1016/j.str.2021.03.016. Epub 2021 Apr 14.
P5, also known as PDIA6, is a PDI family member involved in the ER quality control. Here, we revealed that P5 dimerizes via a unique adhesive motif contained in the N-terminal thioredoxin-like domain. Unlike conventional leucine zipper motifs with leucine residues every two helical turns on ∼30-residue parallel α helices, this adhesive motif includes periodic repeats of leucine/valine residues at the third or fourth position spanning five helical turns on 15-residue anti-parallel α helices. The P5 dimerization interface is further stabilized by several reciprocal salt bridges and C-capping interactions between protomers. A monomeric P5 mutant with the impaired adhesive motif showed structural instability and local unfolding, and behaved as aberrant proteins that induce the ER stress response. Disassembly of P5 to monomers compromised its ability to inactivate IRE1α via intermolecular disulfide bond reduction and its Ca-dependent regulation of chaperone function in vitro. Thus, the leucine-valine adhesive motif supports structure and function of P5.
P5，也被称为PDIA6，是参与内质网质量控制的蛋白质二硫键异构酶（PDI）家族成员。在此，我们发现P5通过其N端类硫氧还蛋白结构域中包含的独特黏附基序形成二聚体。与传统的亮氨酸拉链基序不同，传统亮氨酸拉链基序在约30个残基的平行α螺旋上每两个螺旋圈含有亮氨酸残基，而这种黏附基序在15个残基的反平行α螺旋上跨越五个螺旋圈的第三或第四位置包含亮氨酸/缬氨酸残基的周期性重复。P5二聚化界面通过原聚体之间的几个相互的盐桥和C端封端相互作用进一步稳定。具有受损黏附基序的单体P5突变体表现出结构不稳定性和局部解折叠，并表现为诱导内质网应激反应的异常蛋白。P5解聚为单体损害了其通过分子间二硫键还原使肌醇需求酶1α（IRE1α）失活的能力及其在体外对伴侣功能的钙依赖性调节。因此，亮氨酸 - 缬氨酸黏附基序支持P5的结构和功能。
