Four new postsynaptic neurotoxins from Naja naja sputatrix venom: cDNA cloning, protein expression, and phylogenetic analysis.

cDNAs encoding 4 short chain alpha-neurotoxins from Malayan spitting cobra (Naja naja sputatrix) venom were cloned and expressed in Escherichia coli. The recombinant toxins possessed identical amino acid sequences to alpha-neurotoxins. This is the first report on cloning and expression of isoforms of neurotoxins from a species of spitting cobra. Two of these isoforms were also identified in the crude venom by reverse phase-high performance liquid chromatography (RP-HPLC), capillary electrophoresis followed by mass spectrometry and characterized by protein sequencing. Based on the variable amino acid residues, the neurotoxins in N. n. sputatrix could be assigned to 2 major groups, 10E11T and 10Q11A, which could be further subdivided into 10E11T28S: 10E11T28G and 10Q11A28S; 10Q11A28G respectively. These substitutions were also found to be unique to N. n. sputatrix neurotoxins. Phylogenetic analysis based on molecular properties of the toxins provided further support for the classification of N. n. sputatrix neurotoxin into 2 fundamental groups.