期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 288, 期 15, 页码 10759-10765出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.R112.436550
关键词
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资金
- European Union FP7 Program EDICT
- Danish Research Council Program DANSCATT
- Danish Medical Research Council
- Carlsberg fellowship
- Danish Research Council
- Novo-Nordisk Foundation
- European Research Council
The sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) is a transmembrane ion transporter belonging to the P-II-type ATPase family. It performs the vital task of re-sequestering cytoplasmic Ca2+ to the sarco/endoplasmic reticulum store, thereby also terminating Ca2+-induced signaling such as in muscle contraction. This minireview focuses on the transport pathways of Ca2+ and H+ ions across the lipid bilayer through SERCA. The ion-binding sites of SERCA are accessible from either the cytoplasm or the sarco/endoplasmic reticulum lumen, and the Ca2+ entry and exit channels are both formed mainly by rearrangements of four N-terminal transmembrane alpha-helices. Recent improvements in the resolution of the crystal structures of rabbit SERCA1a have revealed a hydrated pathway in the C-terminal transmembrane region leading from the ion-binding sites to the cytosol. A comparison of different SERCA conformations reveals that this C-terminal pathway is exclusive to Ca2+-free E2 states, suggesting that it may play a functional role in proton release from the ion-binding sites. This is in agreement with molecular dynamics simulations and mutational studies and is in striking analogy to a similar pathway recently described for the related sodium pump. We therefore suggest a model for the ion exchange mechanism in P-II-ATPases including not one, but two cytoplasmic pathways working in concert.
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