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Three-dimensional structure of the KChIP1–Kv4.3 T1 complex reveals a cross-shaped octamer

Abstract

Brain IA and cardiac Ito currents arise from complexes containing Kv4 voltage-gated potassium channels and cytoplasmic calcium-sensor proteins (KChIPs). Here, we present X-ray crystallographic and small-angle X-ray scattering data that show that the KChIP1–Kv4.3 N-terminal cytoplasmic domain complex is a cross-shaped octamer bearing two principal interaction sites. Site 1 comprises interactions between a unique Kv4 channel N-terminal hydrophobic segment and a hydrophobic pocket formed by displacement of the KChIP H10 helix. Site 2 comprises interactions between a T1 assembly domain loop and the KChIP H2 helix. Functional and biochemical studies indicate that site 1 influences channel trafficking, whereas site 2 affects channel gating, and that calcium binding is intimately linked to KChIP folding and complex formation. Together, the data resolve how Kv4 channels and KChIPs interact and provide a framework for understanding how KChIPs modulate Kv4 function.

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Figure 1: Structure of the KChIP1–Kv4.3 T1 complex.
Figure 2: Details of KChIP1–Kv4.3 T1N and T1 domain interactions.
Figure 3: SAXS analysis of the KChIP1–Kv4.3 T1 complex.
Figure 4: Effects of site 2 mutations on KChIP1–Kv4.3 channel modulation and complex formation.
Figure 5: Calcium effects on KChIP1–Kv4.3 complex formation and channel modulation.
Figure 6: Model of a Kv4.3–KChIP channel complex.

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Acknowledgements

We thank D. Julius and F. Van Petegem for comments on the manuscript, J. Holton at ALS beamline 8.3.1 for data collection help, L.Y. Jan (University of California San Francisco) for the Kv4.3 clone and Minor laboratory members for support. This work was supported by awards to D.L.M. from the McKnight Foundation for Neuroscience, Rita Allen Foundation, Searle Scholars Award, Arnold and Mabel Beckman Foundation and US National Institutes of Health. G.L.H. was supported by US National Cancer Institute grant CA92584 and US Department of Energy contract DE-AC03-76SF00098. D.L.M. is a McKnight Scholar, Rita Allen Scholar, Searle Scholar and Beckman Young Investigator.

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Correspondence to Daniel L Minor, Jr.

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Supplementary information

Supplementary Fig. 1

Monomer of the KChIP1-T1N fusion, superposition of frequenin EF2 and KChIP1 EF2 and frequenin structure. (PDF 91 kb)

Supplementary Fig. 2

T1N helix and linker structure. (PDF 562 kb)

Supplementary Fig. 3

Solution analysis of the KChIP1–Kv4.3 T1 complex. (PDF 113 kb)

Supplementary Fig. 4

Gel-filtration elution profiles for purified KChIP37–216 and EF mutants. (PDF 186 kb)

Supplementary Methods (PDF 59 kb)

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Pioletti, M., Findeisen, F., Hura, G. et al. Three-dimensional structure of the KChIP1–Kv4.3 T1 complex reveals a cross-shaped octamer. Nat Struct Mol Biol 13, 987–995 (2006). https://doi.org/10.1038/nsmb1164

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