Kaliotoxin (1-37) shows structural differences with related potassium channel blockers

Analysis of the three-dimensional structure of kaliotoxin (1-37), KTX(1-37) a calcium-dependent potassium channel inhibiting toxin, reveals the presence of proteins in the alpha-helices, implying structural differences that might be associated with selectivity. The shorter helical region disordered by the presence of two prolines differentiates KTX(1-37) from its otherwise homologous toxin charybdotoxin (ChTx). The disordering causes a bending of alpha-helix and the 3(sub 10) helix turn in the last three residues. The extended structure occurring prior to the helix prefers an alternate packing of this region, which affects the accessibility of 27Lys involved in channel blocking.