Renaturation of a reduced Taiwan cobra cardiotoxin.

Refolding of a denatured protein obtained by reducing cardiotoxin from the Taiwan cobra with mercaptoethanol has been carried out in aqueous and non-aqueous solutions. Oxidation of the reduced protein in 0.05 M phosphate buffer (pH 7.2) resulted in isolating an active protein which showed, as compared to native cardiotoxin, identical conformation and biological activities such as lethality, antigenicity and muscle contracture inducing activity. On the other hand, the reduced protein was undergoing incorrect SS-pairing and several inactive products were formed in a mixture of 1,2-ethanediol and 1-propanol (1 : 1; v/v).