The utility of toxins in biomedical research, diagnosis, and therapy is widely recognized. Unfortunately their use is limited by an inadequate target discrimination. Thus, the search for target-specific toxins is of primary relevance. The fact that despite the incredible number of toxins present in the animal kingdom, only a limited number of molecular scaffolds has been selected, is a clear evidence of the importance of the nature and spatial orientation the side chains. The description and understanding of the contact surface between the toxin and the channel entrance appears to be the target for the rationale design of selective and high affinity drugs. Tc32 toxin from the scorpion Tityus cambridgei has been reported to have a clear inhibitory effect on Kv1.3 K channel [1]. This channel, member of the Shaker family [2], carries a large proportion of the outward current not only in leucocytes [3] but also in a variety of neuronal cells [4]. In the present work, Tc32 has been cloned and expressed in a soluble and active form for the first time, employing a new protocol we devised [5]. Tc32 activity has been characterized by electrophysiological assays on a distinct subpopulation of periglomerular cells of olfactory bulb and its 3D solution structure determined by 1HNMR spectroscopy. The structure reveals it exhibits an α/β scaffold typical of the members of the α-KTx family. A structural comparison with the other members of α- KTx 18 subfamily is presented following molecular modeling calculations, and docking simulations to Kv1.1 and Kv1.3 channels. Our data point out Tc32 as a good lead molecule for the development of new molecules suited for research, diagnosis and therapy.
Insights on channel selectivity from the structural and functional characterization of the Kv1.3 channel blocker Tc32
PIGNATELLI, Angela;BELLUZZI, Ottorino;
2011
Abstract
The utility of toxins in biomedical research, diagnosis, and therapy is widely recognized. Unfortunately their use is limited by an inadequate target discrimination. Thus, the search for target-specific toxins is of primary relevance. The fact that despite the incredible number of toxins present in the animal kingdom, only a limited number of molecular scaffolds has been selected, is a clear evidence of the importance of the nature and spatial orientation the side chains. The description and understanding of the contact surface between the toxin and the channel entrance appears to be the target for the rationale design of selective and high affinity drugs. Tc32 toxin from the scorpion Tityus cambridgei has been reported to have a clear inhibitory effect on Kv1.3 K channel [1]. This channel, member of the Shaker family [2], carries a large proportion of the outward current not only in leucocytes [3] but also in a variety of neuronal cells [4]. In the present work, Tc32 has been cloned and expressed in a soluble and active form for the first time, employing a new protocol we devised [5]. Tc32 activity has been characterized by electrophysiological assays on a distinct subpopulation of periglomerular cells of olfactory bulb and its 3D solution structure determined by 1HNMR spectroscopy. The structure reveals it exhibits an α/β scaffold typical of the members of the α-KTx family. A structural comparison with the other members of α- KTx 18 subfamily is presented following molecular modeling calculations, and docking simulations to Kv1.1 and Kv1.3 channels. Our data point out Tc32 as a good lead molecule for the development of new molecules suited for research, diagnosis and therapy.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
