The voltage-sensitive sodium channels are responsible for initiating action potentials in electrically excitable cells such as nerves and muscles. This means they are a critical link in the chain of cellular-level events that produce movement and sensation, and even thought and emotion. This article presented the first three-dimensional view of the sodium-channel protein.
Abstract from: Nature 409, 1047-1051 (22 February 2001)
Chikara Sato*, Yutaka Ueno*, Kiyoshi Asai*, Katsutoshi Takahashi², Masahiko Sato³, Andreas Engel§ & Yoshinori Fujiyoshi║
Voltage-sensitive membrane channels, the sodium channel, the potassium channel and the calcium channel operate together to amplify, transmit and generate electric pulses in higher forms of life. Sodium and calcium channels are involved in cell excitation, neuronal transmission, muscle contraction and many functions that relate directly to human diseases. Sodium channels-glycosylated proteins with a relative molecular mass of about 300,000, are responsible for signal transduction and amplification, and are chief targets of anaesthetic drugs and neurotoxins. Here we present the three-dimensional structure of the voltage-sensitive sodium channel from the eel Electrophorus electricus. The 19 Å resolution structure was determined by cryo-electron microscopy and single-particle image analysis of the solubilized sodium channel. The channel has a bell-shaped outer surface of 135 Å in height and 100 Å in side length at the squareshaped bottom, and a spherical top with a diameter of 65 Å. Several inner cavities are connected to four small holes and eight orifices close to the extracellular and cytoplasmic membrane surfaces. Homologous voltage-sensitive calcium and tetrameric potassium channels, which regulate secretory processes and the membrane potential, may possess a related structure.