Electron Diffraction Study of Crotoxin Complex At 1.6 Å

Abstract

Crotoxin complex is the principle neurotoxin isolated from the rattlesnake venom of Crotalus d. terrificius [1]. The crotoxin complex can be dissociated by 6 M urea into two dissimilar subunits of 14,000 and 10,000 daltons respectively [2,3]. The large subunit is denoted as crotoxin B with a pl of 8.4 and the small subunit is denoted as crotoxin A with a pl of 3.8. Since the pl of the crotoxin complex is 4.5, the positively charged groups in crotoxin B are apparently neutralized due to the interaction of the two subunits. [4]. One of the biological activities of crotoxin complex and of crotoxin B is to catalyze the enzymatic degradation of phospholipids is as the phospholipase A2 isolated from other sources [5]. The recent amino acid sequence results show some sequence homology between crotoxin B and other toxic and nontoxic phospholipases [6]. Both the crotoxin A and B subunits contain 7 disulphide bridges as in some other neurotoxins from snake venoms [7]. Fluorescence emission spectroscopy has been used to show the conformational changes upon the Separation of the two subunits [8].