Characterization of voltage-dependent calcium channel blocking peptides from the venom of the tarantula Grammostola rosea

Toxicon. 2011 Sep 1;58(3):265-76. doi: 10.1016/j.toxicon.2011.06.006. Epub 2011 Jun 28.

Abstract

Voltage-dependent calcium channel blocking peptides were purified and sequenced from the venom of the tarantula, Grammostola rosea. cDNAs encoding the peptide sequences were cloned from the venom gland cDNA library. The electrophysiological effects of the peptides on several types of voltage-dependent calcium channels were evaluated using a Xenopus laevis oocyte expression system. A peptide contained in one of the HPLC peak fractions inhibited P/Q type voltage-dependent calcium channels (Ca(v)2.1). The amino acid sequence of this peptide is identical to that of ω-grammotoxin SIA. A peptide from another discrete peak, which is identical to GsAFII except for one tryptophan residue in the C-terminus, inhibited L-type voltage-dependent calcium channels (Ca(v)1.2). A novel peptide, named GTx1-15 (Accession number, AB201016), shows 76.5% sequence homology with the sodium channel blocker phrixotoxin 3, however, GTx1-15 preferentially inhibited T-type voltage-dependent calcium channels (Ca(v)3.1). In silico secondary and tertiary structure prediction revealed that GTx1-15 and sodium channel blockers such as hainantoxin-IV, phrixotoxin 3, and ceratotoxin 2 show very similar β-strand composition, distribution of Optimal Docking Areas (continuous surface patches likely to be involved in protein-protein interactions), and surface electrostatic potential. These findings suggest that these peptide toxins evolved from common ancestors by gene duplication to maintain surface atmospheres appropriate for interaction with low-voltage-dependent ion channels.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Calcium Channel Blockers / chemistry
  • Calcium Channel Blockers / isolation & purification
  • Calcium Channel Blockers / pharmacology*
  • Calcium Channels, N-Type / metabolism*
  • Calcium Channels, T-Type / metabolism
  • Cloning, Molecular
  • DNA, Complementary / chemistry
  • Female
  • Molecular Sequence Data
  • Peptides / chemistry
  • Peptides / isolation & purification
  • Peptides / pharmacology*
  • Protein Structure, Tertiary
  • Sodium Channel Blockers / pharmacology
  • Spider Venoms / chemistry*
  • Static Electricity
  • Xenopus

Substances

  • Cacna1g protein, rat
  • Calcium Channel Blockers
  • Calcium Channels, N-Type
  • Calcium Channels, T-Type
  • DNA, Complementary
  • Peptides
  • Sodium Channel Blockers
  • Spider Venoms
  • voltage-dependent calcium channel (P-Q type)