1hvw
From Proteopedia
HAIRPINLESS MUTANT OF OMEGA-ATRACOTOXIN-HV1A
Structural highlights
Function[TOT1A_HADVE] Reversibly and voltage-independently blocks both mid-low- (M-LVA) and high-voltage-activated (HVA) calcium channels in cockroach DUM neurons. Lethal to many insect orders but not toxic to mice or rabbits. May target the insect high-voltage-activated calcium channel Dmca1D. Also inhibits acarines calcium channels. An extremely high toxin concentration partially inhibits Cav1.2/CACNA1C, Cav2.1/CACNA1A and Cav2.2/CACNA1B calcium channel of rats. As for omega-AcTx-Hv2a, the phenotypic effect of injection of this toxin into lone star ticks (Amblyomma americanum) is curling of all eight legs into closed loops.[1] [2] [3] [4] [5] Publication Abstract from PubMedomega-Atracotoxin-Hv1a is an insect-specific neurotoxin whose phylogenetic specificity derives from its ability to antagonize insect, but not vertebrate, voltage-gated calcium channels. In order to help understand its mechanism of action and to enhance its utility as a lead compound for insecticide development, we used a combination of protein engineering and site-directed mutagenesis to probe the toxin for key functional regions. First, we constructed a Hairpinless mutant in which the C-terminal beta-hairpin, which is highly conserved in this family of neurotoxins, was excised without affecting the fold of the residual disulfide-rich core of the toxin. The Hairpinless mutant was devoid of insecticidal activity, indicating the functional importance of the hairpin. We subsequently developed a highly efficient system for production of recombinant toxin and then probed the hairpin for key functional residues using alanine-scanning mutagenesis followed by a second round of mutagenesis based on initial "hits" from the alanine scan. This revealed that two spatially proximal residues, Asn(27) and Arg(35), form a contiguous molecular surface that is essential for toxin activity. We propose that this surface of the beta-hairpin is a key site for interaction of the toxin with insect calcium channels. Functional significance of the beta hairpin in the insecticidal neurotoxin omega-atracotoxin-Hv1a.,Tedford HW, Fletcher JI, King GF J Biol Chem. 2001 Jul 13;276(28):26568-76. Epub 2001 Apr 19. PMID:11313356[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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