Biochemical studies on scorpion (Mesobuthus tamulus) and bee (Apis mellifera) venom peptides.

Animal venoms are essentially diverse libraries of compounds evolved to have both high affinity and high specificity, making them ideal targets for bioprospecting. Despite advances in antivenom therapy, envenomations remain clinically significant, accounting for numerous human fatalities.The Indian red scorpion (Mesobuthus tamulus) is a serious threat to life in India, but its venom is poorly characterised. This study examines antigenic and proteomic variability of Mesob. tamulus venoms obtained in two geographical regions with distinct biotopes. In addition to highlighting general venomic differences between the two populations, the study identified a peptide of 2947Da that may prove diagnostic between the venom types. As an aid to the future isolation of specific peptides, particularly those initially identified via their DNA sequences, a mass profile of fractionated, commercially available venom was also generated.Scorpion short insectotoxins may have importance as chloride channel blockers and in cancer therapeutics. Only a few such molecules have been isolated and in general, relatively little is known about their properties. Analysis of a Mesob. tamulus telson cDNA library, using probes based upon the signal peptide sequence of a known short insectotoxin (Bm12 from Buthus martensii), yielded two novel "short-insectotoxin" sequences, BtCh11 and BtChl2. Mass spectrometry-guided isolation has been used to purify a corresponding peptide from the venom, based upon its calculated mass. Additional studies using the same cDNA revealed evidence supporting the amidation of tamulustoxin (a potassium channel toxin found in the venom of this species), and evidence to suggest the existence of a novel long-chain potassium channel toxin.Toxins also play an important role as molecular probes for the dissection of ion channel structure. The structure-function relationships of apamin (a calcium-activated potassium channel toxin from the honey bee, Apis mellifera) were examined by investigating the effect of addition of a fluorescent label, non-native disulphide pairings, and disruption of the B-tum on the toxin's affinity for its receptor on rat brain membranes.