The isolation and characterization of a peptide that alters sodium channels from Buthus martensii Karsch

Modulation of intracellular Na+ concentration by BmK AS, a scorpion toxin, in B104 cell line

ABSL Effects of BmK AS, a toxin from scorpion Buthus mortensi Karsch and an activator of skeletal muscle RyRs, on the intracellular Na+ concentration have been investigated in the B104 neuroblastoma cell line by fluorescence digital imaging techniques. The intracellular Na+ concentration was elevated by 500 nM BmK AS significantly over a 30 min period, and the effect could be enhanced by addition of ouabain. In addition, BmK AS induced a biphasic modulation of [Na+]i in the dose-dependent range from 20 to 500 nM in the presence of ouabain. The results suggest that BmK AS may modulate intracellular signals by altering the intracellular Na+ concentration in the B104 cells.

An overview of toxins and genes from the venom of the Asian scorpion Buthus martensi Karsch

Among the different scorpion species, Buthus martensi Karsch (BmK), a widely distributed scorpion species in Asia, has received a lot of attention. Indeed, over the past decade, more than 70 different peptides, toxins or homologues have been isolated and more peptides are probably still to be revealed. This review is focusing on the many peptides isolated from the venom of this scorpion, their targets, their genes and their structures. The aim is to give both a 'state of the art' view of the research on BmK venom and an illustration of the complexity of this scorpion venom. In the present manuscript, we have listed the different ion channel toxins and homologues isolated from the venom of BmK, either from the literature or from databases. We have described here 51 long-chain peptides related to the Na(+) channel toxins family: 34 related to the alpha-toxin family, four related to the excitatory insect toxin family, 10 related to the depressant insect toxin, one beta-like toxin plus two peptides, BmK AS and AS1, that act on ryanodine receptors. We also listed 18 peptides related to the K(+) channel toxin family: 14 short chain toxins or homologues, two long chain K(+) toxin homologues and two putative K(+) toxin precursors. Additionally, two chlorotoxin like peptides (Bm-12 and 12 b) have been isolated in the venom of BmK. Besides these ion channels toxins, two peptides without disulfide bridges (the bradykinin-potentiating peptide BmK bpp and BmK n1) and three peptides with no known functions have also been discovered in this venom. We have also taken the opportunity of this review to update the classification of scorpion K(+) toxins () which now presents 17 subfamilies instead of the 12 described earlier. The work on the venom of BmK led to the discovery of two new subfamilies, alpha-KT x 14 and alpha-KT x 17.

The isolation and purification of two peptides from the venom of Buthus martensii Karsch

Two peptides that extensively prolong action potentials (APs) in rat and frog nerves have been isolated and purified from the venom of the scorpion Buthus martensii Karsch (BMK). The peptides were purified using gel filtration, ion exchange, FPLC, and HPLC chromatography. Action potentials recorded in the presence of nanomolar concentrations of the peptides were extensively prolonged without much attenuation in their heights. The N-terminal sequences of both the peptides, BMK 9(3)-1 and BMK 9(3)-2, were determined. The N-terminal sequences of BMK 9(3)-1 and BMK 9(3)-2 were found to be: GRDAYIADSEN-PYF-GANPN and GRDAYIADSEN-PYT-ALNP. Sequence similarity comparisons to other alpha-scorpion toxins suggest that the two blanks in each of the sequences are cysteines. The first 20 residues of the two BMK peptides differ by only three amino acid substitutions. The molecular weight (MW) of BMK 9(3)-1 and BMK 9(3)-2 were determined by LC/MS/MS to be 7020 and 7037 Da. Since both of the peptides prolong APs when both K(+) and Ca(++) channels are blocked and show sequence similarity to other alpha-neurotoxins, it appears likely that BMK 9(3)-1 and BMK 9(3)-2 act to alter Na channel inactivation to produce their effects. The first 20 residues of BMK 9(3)-2 are identical to those observed for makatoxin I, a toxin isolated from Buthus martensii Karsch venom, that alters nitric oxide transmitter release. Since the two toxins also have very similar molecular weights, BMK 9(3)-2 may be identical to makatoxin I; however, BMK 9(3)-2 acts to alter Na channels to exert its effect, thus the two toxins may differ, or if they are identical, they can exert effects on both neural transmission and AP propagation.