Proposed tertiary structure of the sodium channel.

On the basis of our recent results of the complete amino acid sequence of the squid Loligo bleekeri sodium channel deduced by cloning and sequence analysis of the complementary DNA (Sato, C. and Matsumoto, G. Biochem. Biophys. Res. Comm. 186, 1), we have proposed a tertiary structure model of the sodium channel where the transmembrane segments are octagonally aligned and the four linkers of S5-6 between segments S5 and S6 play a crucial role in the activation gate, voltage sensor and ion selective pore, which can slide, depending on membrane potentials, along inner walls consisting of segments S2 and S4 alternately. The proposed model is contrasted with that of Noda et al. (Nature 320; 188-192, 1986).