Open AccessIdentification of a novel binding site for calmodulin in ammodytoxin A, a neurotoxic group IIA phospholipase A 2
Author(s) -
Prijatelj Petra,
Šribar Jernej,
Ivanovski Gabriela,
Križaj Igor,
Gubenšek Franc,
Pungerčar Jože
Publication year - 2003
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1046/j.1432-1033.2003.03679.x
Subject(s) - venom , chemistry , calmodulin , binding site , phospholipase , stereochemistry , toxin , biochemistry , neurotoxicity , toxicity , enzyme , organic chemistry
The molecular mechanism of the presynaptic neurotoxicity of snake venom phospholipases A 2 (PLA 2 s) is not yet fully elucidated. Recently, new high‐affinity binding proteins for PLA 2 toxins have been discovered, including the important intracellular Ca 2+ sensor, calmodulin (CaM). In the present study, the mode of interaction of group IIA PLA 2 s with the Ca 2+ ‐bound form of CaM was investigated by mutational analysis of ammodytoxin A (AtxA) from the long‐nosed viper ( Vipera ammodytes ammodytes ). Several residues in the C‐terminal part of AtxA were found to be important in this interaction, particularly those in the region 115–119. In support of this finding, introduction of Y115, I116, R118 and N119, present in AtxA, into a weakly neurotoxic PLA 2 from Russell's viper ( Daboia russellii russellii ) increased by sevenfold its binding affinity for CaM. Furthermore, two out of four peptides deduced from different regions of AtxA were able to compete with the toxin in binding to CaM. The nonapeptide showing the strongest inhibition was that comprising the AtxA region 115–119. This stretch contributes to a distinct hydrophobic patch within the region 107–125 in the C‐terminal part of the molecule. This lacks any substantial helical structure and is surrounded by several basic residues, which may form a novel binding motif for CaM on the molecular surface of the PLA 2 toxin.