National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
R35GM144109
米国
Danish Council for Independent Research
0135-00032B
デンマーク
The Carlsberg Foundation
CF19-0127
デンマーク
引用
ジャーナル: Proc Natl Acad Sci U S A / 年: 2024 タイトル: Conformational changes in the Niemann-Pick type C1 protein NCR1 drive sterol translocation. 著者: Kelly M Frain / Emil Dedic / Lynette Nel / Anastasiia Bohush / Esben Olesen / Katja Thaysen / Daniel Wüstner / David L Stokes / Bjørn Panyella Pedersen / 要旨: The membrane protein Niemann-Pick type C1 (NPC1, named NCR1 in yeast) is central to sterol homeostasis in eukaryotes. NCR1 is localized to the vacuolar membrane, where it is suggested to carry ...The membrane protein Niemann-Pick type C1 (NPC1, named NCR1 in yeast) is central to sterol homeostasis in eukaryotes. NCR1 is localized to the vacuolar membrane, where it is suggested to carry sterols across the protective glycocalyx and deposit them into the vacuolar membrane. However, documentation of a vacuolar glycocalyx in fungi is lacking, and the mechanism for sterol translocation has remained unclear. Here, we provide evidence supporting the presence of a glycocalyx in isolated vacuoles and report four cryo-EM structures of NCR1 in two distinct conformations, named tense and relaxed. These two conformations illustrate the movement of sterols through a tunnel formed by the luminal domains, thus bypassing the barrier presented by the glycocalyx. Based on these structures and on comparison with other members of the Resistance-Nodulation-Division (RND) superfamily, we propose a transport model that links changes in the luminal domains with a cycle of protonation and deprotonation within the transmembrane region of the protein. Our model suggests that NPC proteins work by a generalized RND mechanism where the proton motive force drives conformational changes in the transmembrane domains that are allosterically coupled to luminal/extracellular domains to promote sterol transport.