Structural basis of the α1–β subunit interaction of voltage-gated Ca2+ channels

Abstract

High-voltage-activated Ca2+ channels are essential for diverse biological processes. They are composed of four or five subunits, including α1, α2-δ, β and γ (ref. 1). Their expression and function are critically dependent on the β-subunit, which transports α1 to the surface membrane and regulates diverse channel properties2,3,4. It is believed3,4,5,6 that the β-subunit interacts with α1 primarily through the β-interaction domain (BID), which binds directly to the α-interaction domain (AID) of α17; however, the molecular mechanism of the α1–β interaction is largely unclear. Here we report the crystal structures of the conserved core region of β3, alone and in complex with AID, and of β4 alone. The structures show that the β-subunit core contains two interacting domains: a Src homology 3 (SH3) domain and a guanylate kinase (GK) domain. The AID binds to a hydrophobic groove in the GK domain through extensive interactions, conferring extremely high affinity between α1 and β-subunits4,8. The BID is essential both for the structural integrity of and for bridging the SH3 and GK domains, but it does not participate directly in binding α1. The presence of multiple protein-interacting modules in the β-subunit opens a new dimension to its function as a multi-functional protein.

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Figure 1: Sequence alignment and domain organization of Ca2+ channel α1 and β-subunits.
Figure 2: Crystal structure of the β3 core in complex with its α1 binding partner (AID).
Figure 3: Interactions between β3 and AID.
Figure 4: Structural comparisons of the β-subunit core.
Figure 5: Structural and functional comparisons of the β-subunit with other proteins.

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Acknowledgements

We thank Y. Mori for CaV2.1 complementary DNA; E. Perez-Reyes for all β-subunit cDNAs; T. Tanabe for α2δ cDNA; and the staff at X4A of NSLS, Brookhaven National Laboratory, for synchrotron support. This work was supported by grants to L.T. and J.Y. from the National Institutes of Health. J.Y. is a recipient of the McKnight Scholar Award, the Scholar Research Programme of the EJLB Foundation and the Established Investigator Award of the American Heart Association.

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Correspondence to Jian Yang.

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Supplementary information

Supplementary Figure 1

Comparison of the structures of the core region of Ca2+ channel β subunits. (DOC 2325 kb)

Supplementary Figure 2

BID is not directly involved in binding AID. (DOC 784 kb)

Supplementary Figure 3

Stimulation of Ca2+ channel expression by an artificial peptide. (DOC 530 kb)

Supplementary Figure 4

Quality of structural models. (DOC 1782 kb)

Supplementary Table 1

Crystallographic Data, phasing statistics, and refinement statistics. (DOC 43 kb)

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Chen, Y., Li, M., Zhang, Y. et al. Structural basis of the α1–β subunit interaction of voltage-gated Ca2+ channels. Nature 429, 675–680 (2004). https://doi.org/10.1038/nature02641

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