National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
P20GM103546
米国
National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
R01GM105993
米国
National Science Foundation (NSF, United States)
1738547
米国
引用
ジャーナル: Nat Commun / 年: 2020 タイトル: Structure of the G protein chaperone and guanine nucleotide exchange factor Ric-8A bound to Gαi1. 著者: Levi J McClelland / Kaiming Zhang / Tung-Chung Mou / Jake Johnston / Cindee Yates-Hansen / Shanshan Li / Celestine J Thomas / Tzanko I Doukov / Sarah Triest / Alexandre Wohlkonig / Gregory G ...著者: Levi J McClelland / Kaiming Zhang / Tung-Chung Mou / Jake Johnston / Cindee Yates-Hansen / Shanshan Li / Celestine J Thomas / Tzanko I Doukov / Sarah Triest / Alexandre Wohlkonig / Gregory G Tall / Jan Steyaert / Wah Chiu / Stephen R Sprang / 要旨: Ric-8A is a cytosolic Guanine Nucleotide exchange Factor (GEF) that activates heterotrimeric G protein alpha subunits (Gα) and serves as an essential Gα chaperone. Mechanisms by which Ric-8A ...Ric-8A is a cytosolic Guanine Nucleotide exchange Factor (GEF) that activates heterotrimeric G protein alpha subunits (Gα) and serves as an essential Gα chaperone. Mechanisms by which Ric-8A catalyzes these activities, which are stimulated by Casein Kinase II phosphorylation, are unknown. We report the structure of the nanobody-stabilized complex of nucleotide-free Gα bound to phosphorylated Ric-8A at near atomic resolution by cryo-electron microscopy and X-ray crystallography. The mechanism of Ric-8A GEF activity differs considerably from that employed by G protein-coupled receptors at the plasma membrane. Ric-8A engages a specific conformation of Gα at multiple interfaces to form a complex that is stabilized by phosphorylation within a Ric-8A segment that connects two Gα binding sites. The C-terminus of Gα is ejected from its beta sheet core, thereby dismantling the GDP binding site. Ric-8A binds to the exposed Gα beta sheet and switch II to stabilize the nucleotide-free state of Gα.