Isolation and Primary Structure of Bombyxin-IV, a Novel Molecular Species of Bombyxin from the Silkworm, Bombyx mori

Abstract

From 1.2 × 10⁶ male adult heads of the silkworm, Bombyx mori, 0.16 mg of bombyxin-IV was isolated, which was a novel molecular species of bombyxin, previously called 4K-prothoracicotropic hormone. Injection of 0.1 ng of bombyxin-IV into a dauer pupa of the Eri-silkworm, Samia cynthia ricini, evoked adult development. Microsequencing, chemical modification, enzymatic digestion, and fast atom bombardment mass spectrometry showed that bombyxin-IV consisted of two heterogeneous peptides linked by disulfide bonds and had a considerable sequence homology (62.5%) with bombyxin-II.