Strathprints Home | Open Access | Browse | Search | User area | Copyright | Help | Library Home | SUPrimo

Delineation of the functional site of alpha-dendrotoxin - the functional topographies of dendrotoxins are different but share a conserved core with those of other kv1 potassium channel-blocking toxins

Gasparini, S. and Danse, J.M. and Lecoq, A. and Pinkasfeld, S. and Zinn-Justin, S. and Young, L.C. and de Medeiros, C.C.L. and Rowan, E.G. (1998) Delineation of the functional site of alpha-dendrotoxin - the functional topographies of dendrotoxins are different but share a conserved core with those of other kv1 potassium channel-blocking toxins. Journal of Biological Chemistry, 273 (39). pp. 25393-25403. ISSN 0021-9258

Full text not available in this repository. (Request a copy from the Strathclyde author)

Abstract

We identified the residues that are important for the binding of α-dendrotoxin (αDTX) to Kv1 potassium channels on rat brain synaptosomal membranes, using a mutational approach based on site-directed mutagenesis and chemical synthesis. Twenty-six of its 59 residues were individually substituted by alanine. Substitutions of Lys5 and Leu9 decreased affinity more than 1000-fold, and substitutions of Arg3, Arg4, Leu6, and Ile8 by 5-30-fold. Substitution of Lys5 by norleucine or ornithine also greatly altered the binding properties of αDTX. All of these analogs displayed similar circular dichroism spectra as compared with the wild-type αDTX, indicating that none of these substitutions affect the overall conformation of the toxin. Substitutions of Ser38 and Arg46 also reduced the affinity of the toxin but, in addition, modified its dichroic properties, suggesting that these two residues play a structural role. The other residues were excluded from the recognition site because their substitutions caused no significant affinity change. Thus, the functional site of αDTX includes six major binding residues, all located in its N-terminal region, with Lys5 and Leu9 being the most important. Comparison of the functional site of αDTX with that of DTX-K, another dendrotoxin (Smith, L. A., Reid, P. F., Wang, F. C., Parcej, D. N., Schmidt, J. J., Olson, M. A., and Dolly, J. O. (1997)Biochemistry 36, 7690-7696), reveals that they only share the predominant lysine and probably a leucine residue; the additional functional residues differ from one toxin to the other. Comparison of the functional site of αDTX with those of structurally unrelated potassium channel-blocking toxins from venomous invertebrates revealed the common presence of a protruding key lysine with a close important hydrophobic residue (Leu, Tyr, or Phe) and few additional residues. Therefore, irrespective of their phylogenetic origin, all of these toxins may have undergone a functional convergence. The functional site of αDTX is topographically unrelated to the 'antiprotease site' of the structurally analogous bovine pancreatic trypsin inhibitor.

Item type: Article
ID code: 17540
Notes: Strathprints' policy is to record up to 8 authors per publication, plus any additional authors based at the University of Strathclyde. More authors may be listed on the official publication than appear in the Strathprints' record.
Keywords: delineation, alpha-dendrotoxin, kv1 potassium, toxins, Pharmacy and materia medica
Subjects: Medicine > Pharmacy and materia medica
Department: Faculty of Science > Strathclyde Institute of Pharmacy and Biomedical Sciences
Related URLs:
    Depositing user: Strathprints Administrator
    Date Deposited: 30 Apr 2010 10:47
    Last modified: 12 Mar 2012 11:07
    URI: http://strathprints.strath.ac.uk/id/eprint/17540

    Actions (login required)

    View Item