PROPERTIES OF SHAKER-HOMOLOGOUS POTASSIUM CHANNELS EXPRESSED IN THE MAMMALIAN BRAIN

Sixteen different K+ channel subtypes have been cloned from mammalian tissue. Considering their sequence homology to Drosophila Shaker, Shab , Shaw and Shal channels, they were classified into four corresponding classes K(v)1-4. All K+ channels belonging to these classes consist o f four subunits with each six hydrophobic segments (S1-S6) and a chara cteristic structure-function relationship of certain domains in their amino acid sequence. These domains are, the inactivation gate in the N -terminal region of the sequence, the voltage sensor in the fourth hyd rophobic segment (S4), and the pore-region in the H5 segment between S 5 and S6. In some functional properties K+ channels cloned from the ma mmalian brain, however, differ from Drosophila K+ channels. These are pharmacological differences, differences in the threshold of activatio n and in regulation of inactivation. Part of these differences are imp ortant to understand their physiological role in the brain. Based on t heir functional characteristics the expression pattern of cloned K+ ch annels in the rat brain can be correlated with the properties of K+ cu rrents measured in central neurones.