H-Pro-Gly-Thr-Cys-Glu-Ile-Cys-Ala-Tyr-Ala-Ala-Cys-Thr-Gly-Cys-OH (Disulfide bonds between Cys⁴ and Cys¹²/Cys⁷ and Cys¹⁵)