期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 290, 期 50, 页码 30006-30017出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M115.677328
关键词
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资金
- National Science Foundation Graduate Research Fellowship [DGE-1144469]
- National Institutes of Health [5T32GM007616-33, R01GM097572, R01GM107368]
- Gordon and Betty Moore Foundation [GBMF775]
- Beckman Institute
Tail-anchored (TA) proteins, defined as having a single transmembrane helix at their C terminus, are post-translationally targeted to the endoplasmic reticulum membrane by the guided entry of TA proteins (GET) pathway. In yeast, the handover of TA substrates is mediated by the heterotetrameric Get4/Get5 complex (Get4/5), which tethers the co-chaperone Sgt2 to the targeting factor, the Get3 ATPase. Binding of Get4/5 to Get3 is critical for efficient TA targeting; however, questions remain about the formation of the Get3.Get4/5 complex. Here we report crystal structures of a Get3.Get4/5 complex from Saccharomyces cerevisiae at 2.8 and 6.0 angstrom that reveal a novel interface between Get3 and Get4 dominated by electrostatic interactions. Kinetic and mutational analyses strongly suggest that these structures represent an on-pathway intermediate that rapidly assembles and then rearranges to the final Get3.Get4/5 complex. Furthermore, we provide evidence that the Get3.Get4/5 complex is dominated by a single Get4/5 heterotetramer bound to one monomer of a Get3 dimer, uncovering an intriguing asymmetry in the Get4/5 heterotetramer upon Get3 binding. Ultrafast diffusion-limited electrostatically driven Get3.Get4/5 association enables Get4/5 to rapidly sample and capture Get3 at different stages of the GET pathway.
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