PURIFICATION AND CHARACTERIZATION OF A JUVENILE-HORMONE BINDING-PROTEIN FROM HEMOLYMPH OF THE SILKWORM, BOMBYX-MORI

A juvenile hormone binding protein (JHBP) has been isolated from Bomby x mori hemolymph by gel filtration, ion-exchange chromatography, chrom atofocusing and hydroxyapatite column chromatography. Gel electrophore sis indicates that the isolated protein is homogeneous in the presence or absence of a denaturing agent. The JHBP in question has a relative molecular mass of 32 kDa, determined by denaturing gel electrophoresi s, Chromatofocusing analysis indicated that the JHBP is an acidic prot ein with pI 4.9. The protein exhibits a dissociation constant of 9.0 x 10(-8) M for JH I, 1.14 x 10(-7) M for JH II and 3.9 x 10(-7) M for J H III, and thus its affinity for JH analogues is in the order of JH I > JH II > JH III. Its amino acid composition indicates that the protei n consists of 297 residues of 18 kinds of amino acids. The sequence of the N-terminus of the polypeptide chain was determined for 34 of the first 36 residues: he-Leu-Glu-Lys-Thr-Ser-Lys-Gly-Ile-Pro-?-Tyr-His-.