Molecular Biophysics Unit, Indian Institute of Science, Bangalore, 560012, India.
St. Jude Children's Research Hospital, Memphis, TN, USA.
Nat Commun. 2024 Apr 5;15(1):2942. doi: 10.1038/s41467-024-47142-6.
Pannexins are single-membrane large-pore channels that release ions and ATP upon activation. Three isoforms of pannexins 1, 2, and 3, perform diverse cellular roles and differ in their pore lining residues. In this study, we report the cryo-EM structure of pannexin 3 at 3.9 Å and analyze its structural differences with pannexin isoforms 1 and 2. The pannexin 3 vestibule has two distinct chambers and a wider pore radius in comparison to pannexins 1 and 2. We further report two cryo-EM structures of pannexin 1, with pore substitutions W74R/R75D that mimic the pore lining residues of pannexin 2 and a germline mutant of pannexin 1, R217H at resolutions of 3.2 Å and 3.9 Å, respectively. Substitution of cationic residues in the vestibule of pannexin 1 results in reduced ATP interaction propensities to the channel. The germline mutant R217H in transmembrane helix 3 (TM3), leads to a partially constricted pore, reduced ATP interaction and weakened voltage sensitivity. The study compares the three pannexin isoform structures, the effects of substitutions of pore and vestibule-lining residues and allosteric effects of a pathological substitution on channel structure and function thereby enhancing our understanding of this vital group of ATP-release channels.
连接蛋白是一种单分子膜大孔通道，在激活时释放离子和 ATP。三种连接蛋白 1、2 和 3 异构体具有不同的细胞功能，其孔衬残基也不同。在这项研究中，我们报道了连接蛋白 3 的冷冻电镜结构，分辨率为 3.9Å，并分析了其与连接蛋白 1 和 2 结构的差异。与连接蛋白 1 和 2 相比，连接蛋白 3 的前庭具有两个不同的腔室和更宽的孔径。我们进一步报道了连接蛋白 1 的两个冷冻电镜结构，一个是具有模拟连接蛋白 2 孔衬残基的 W74R/R75D 孔取代的结构，分辨率为 3.2Å，另一个是连接蛋白 1 的胚系突变体 R217H 的结构，分辨率为 3.9Å。连接蛋白 1 前庭中阳离子残基的取代导致与通道的 ATP 相互作用倾向降低。跨膜螺旋 3（TM3）中的胚系突变体 R217H 导致部分受限的孔、降低的 ATP 相互作用和减弱的电压敏感性。该研究比较了三种连接蛋白异构体的结构、孔和前庭衬里残基取代的影响以及病理取代对通道结构和功能的变构效应，从而增强了我们对这组重要的 ATP 释放通道的理解。
