期刊
JOURNAL OF ELECTRON MICROSCOPY
卷 59, 期 3, 页码 215-226出版社
OXFORD UNIV PRESS
DOI: 10.1093/jmicro/dfp059
关键词
membrane protein; voltage-dependent ion channel; skeletal muscle; electron microscopy; single particle analysis; negative staining
类别
资金
- New Energy and Industrial Technology Development Organization (NEDO) of Japan
The dihydropyridine receptor (DHPR) is a protein complex that consists of five distinct subunits of alpha(1), alpha(2), beta, gamma and delta and functions as a voltage-dependent L-type Ca2+ channel. Here we purified the alpha(1)-beta complex (similar to 250 kDa) from the rabbit skeletal muscle DHPR and reconstructed its three-dimensional (3D) structure to 38 A resolution by single particle analysis of negative staining electron microscopy. The alpha(1)-beta structure exhibited two unique regions: a pseudo-4-fold petaloid region and an elongated region. X-ray crystallographic models of a homologous voltage-dependent K+ channel and the beta subunit fit well into the individual regions of the alpha(1)-beta structure, revealing that the two regions correspond to the transmembrane alpha(1) and the cytoplasmic beta subunits, respectively. In addition, 3D reconstruction and immuno-electron microscopic analysis performed on the independently purified DHPR demonstrated that the alpha(1)-beta complex was located in the large globular portion of the DHPR, and the N-terminal region of the beta subunit was extended to the leg-shaped protrusion of the DHPR, which includes the alpha(2)delta subunits. Our results propose a model in which the beta subunit may regulate ion channel function by acting as a hinge between alpha(1) and alpha(2)delta subunits of the DHPR.
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