New polypeptide components purified from mamba venom.

New polypeptide components have been isolated from Dendroaspis angusticeps venom using chromatography. Two polypeptides containing 59 and 57 amino acids, called 'DaE1' and 'DaE2' respectively, have been purified to homogeneity and fully sequenced. Spectrometric analysis yielded masses of 6631.5 and 6389.0 Da, respectively. The polypeptides share 98 and 95% identity, respectively, with trypsin inhibitor E (DpE) of Dendroaspis polylepis polylepis. 'DaE' polypeptides inhibit Kv1.1 channels with an IC(50) value in the range of 300 nM. They can be considered as new dendrotoxins, albeit with fairly low affinity as compared to alpha-DTX. 'DaE' polypeptides do not affect Kir2.1 channels.