Juvenile‐hormone‐binding protein from the hemolymph of Galleria mellonella (L)

Abstract

A juvenile-hormone-binding protein (JHBP) has been isolated from Galleria mellonella hemolymph by gel filtration, phosphocellulose chromatography, and by chromatofocusing. The isolated protein is homogenous as judged by column chromatography and gel electrophoresis in the presence and absence of denaturing agent. It has a relative molecular mass of 32,000, Stokes radius 2.4 nm, sedimentation coefficient of 2.3 S, molar absorption coefficient at 280 nm .epsilon. = 2.34 .times. 10-4 M-1 cm-1, and is composed of a single polypeptide chain. Chromatofocusing analysis (pI 8.6) and isoelectric focusing (pI 8.1) indicate that the JHBP is an alkaline protein. Its amino acid composition and fluorescent absorption spectra indicate that the protein does not contain tryptophan residues. The protein exhibits one class of binding sites for juvenile hormone (JH), 0.8 per molecule, with the following dissociation constants: JH I, 8.5 .times. 10-8 M; JH II, 7.2 .times. 10-8 M; JH III, 47 .times. 10-8 M. The JHBP binds (10R, 11S)-JH II enanatiomer with 2.3-times higher affinity then (10S, 11R)-JH II enantiomer. The pH optimum of binding is 7.0.