SECONDARY STRUCTURE, STABILITY AND TETRAMERIZATION OF RECOMBINANT K(V)1.1 POTASSIUM CHANNEL CYTOPLASMIC N-TERMINAL FRAGMENT

The recombinant N-terminal fragment (amino acids 14-162) of a tetramer ic voltage-gated potassium channel (K(V)1.1) has been studied using sp ectroscopic techniques. Evidence is presented that it forms a tetramer in aqueous solution, whereas when solubilised in 1% Triton X-100 it r emains monomeric. The secondary structure content of both monomeric an d tetrameric K(V)1.1 N-terminal fragment has been estimated from FTIR and CD spectroscopy to be 20-25% alpha-helix, 20-25% beta-sheet, 20% t urns and 30-40% random coil. Solubilisation of the protein in detergen t is shown by hydrogen-deuterium exchange analysis to alter tertiary s tructure rather than secondary structure and this may be the determini ng factor in tetramerisation ability. Using molecular modelling we pro pose a supersecondary structure consisting of two structural domains. (C) 1997 Elsevier Science B.V.