Abstract
Dihydropyridine receptor (DHPR), an L-type Ca(2+) channel complex, plays an essential role in muscle contraction, secretion, integration of synaptic input in neurons and synaptic transmission. The molecular architecture of DHPR complex remains elusive. Here we present a 15-Å resolution cryo-electron microscopy structure of the skeletal DHPR/L-type Ca(2+) channel complex. The DHPR has an asymmetrical main body joined by a hook-like extension. The main body is composed of a "trapezoid" and a "tetrahedroid". Homologous crystal structure docking and site-specific antibody labelling revealed that the α1 and α2 subunits are located in the "trapezoid" and the β subunit is located in the "tetrahedroid". This structure revealed the molecular architecture of a eukaryotic Ca(2+) channel complex. Furthermore, this structure provides structural insights into the key elements of DHPR involved in physical coupling with the RyR/Ca(2+) release channel and shed light onto the mechanism of excitation-contraction coupling.