SITE-DIRECTED MUTANTS OF NOXIUSTOXIN REVEAL SPECIFIC INTERACTIONS WITH POTASSIUM CHANNELS

Several site directed mutations mere introduced into a synthetic Noxiu stoxin (NTX) gene. Alanine scanning of the nonapeptide at the N-termin al segment of NTX (threonine 1 (T1) to serine 9 (S9)) was constructed and the recombinant products were obtained in pure form. Additionally, lysine 28 (K28) was changed to arginine (R) or glutamic acid (E), cys teine 29 was changed to alanine, and residues 37-39 (TSr-Asn-Asn) of t he carboxyl end were deleted. The recombinant mutants mere tested for their ability to displace I-125-NTX from rat brain synaptosome membran es, as well as for their efficiency in blocking the activity of K(v)1. 1 K+ channels expressed in Xenopus laevis oocytes. The main results in dicate that residues K6, T8 at the amino end, and K28 and the tripepti de YNN at the carboxyl end are involved in specific interactions of NT X with rat brain and/or K(v)1.1 K+ channels. (C) 1998 Federation of Eu ropean Biochemical Societies.