Purification, characterization and binding interactions of the Chinese-cobra (Naja naja atra) serum antitoxic protein CSAP

Abstract

The characterization of the single-chain protein in Chinese-cobra (Naja naja atra) blood serum, which yields strong specific protection against the venom of the same snake, is reported. The protein, CSAP (cobra serum antitoxic protein), was purified to electrophoretic homogeneity. Over the pH range 5-9 it formed stable complexes with the neuro- and the cardio-toxin of the snake. The molecular size of the CSAP was estimated to be 70.3 +/- 0.3 kDa. Tryptic hydrolysis of CSAP yielded several peptides that were able to bind to the toxin. The native CSAP maximally bound 8 +/- 1 toxin molecules/molecule. Six tryptic fragments, containing 5-39 residues, were sequenced. The longest of these displayed sequence similarity to rat serum albumin. The protective effect of the CSAP was demonstrated in vivo on mice and in vitro by measurement of the rate of haemolysis. Kinetic and thermodynamic parameters of the binding interactions of the neurotoxin and the CSAP were determined from the rates of displacement of 125I-labelled toxin from its complexes with the CSAP by unlabelled toxin by using a DEAE-cellulose filter assay for CSAP-toxin complexes. The toxin molecules rapidly dissociated from one type of site and slowly from a second. The binding capacity and concentration of the CSAP suffice to explain the protective effect of the latter against the toxin.

Proteomic Investigations of Two Pakistani Naja Snake Venoms Species Unravel the Venom Complexity, Posttranslational Modifications, and Presence of Extracellular Vesicles

“…It is possible that upon envenomation cobra serum albumin is responsible or supporting the transportation of other venom proteins in the prey serum. Previous studies have reported Cobra blood serum albumin as an antitoxic protein, having the potential to sequester endogenous toxins [ 151 , 152 ]. Cobra serum albumin was also reported in the venom proteome of N. sumatrana [ 93 ].…”

Coevolution takes the sting out of it: Evolutionary biology and mechanisms of toxin resistance in animals

“…These proteins are distinct from those characterised from mammals, and include those demonstrated to inhibit the haemorrhagic, myotoxic and neurotoxic activity of venom metalloproteinases, phospholipases and neurotoxins secreted in their own venom (e.g. Omori-Satoh et al, 1972;Shao et al, 1993;Wang et al, 1995;Lizano et al, 1997Lizano et al, , 2000Ohkura et al, 1997;Faure, 2000;Perales et al, 2005). It therefore appears likely that these components are present to promote autoresistance (i.e.…”

Interaction of the neurotoxic and nontoxic secretory phospholipases A2 with the crotoxin inhibitor from Crotalus serum

“…Venomous snakes are resistant to their own venom and several natural neutralizing proteins have been identified in their plasma [23]. In particular, PLA 2 inhibitors have been isolated from various snake sera and their primary structures have been determined [23–34]. Ohkura and coworkers [27] have classified the PLA 2 inhibitors into three distinct types (α, β and γ) based on their structural characteristics.…”

“…Venomous snakes are resistant to their own venom and several natural neutralizing proteins have been identified in their plasma [23]. In particular, PLA 2 inhibitors have been isolated from various snake sera and their primary structures have been determined [23±34].…”