Purification and characterization of a juvenile hormone binding protein from the hemolymph of the fourth instar tobacco hornworm, Manduca sexta.

A protein which binds the insect juvenile hormone has been isolated from the hemolymph of the fourth instar tobacco hornworm, Manduca sexta (Lepidoptera). Bioassay and chemical characterization of the bound ligand from the purified binding protein indicates that this molecule is the primary macromolecule responsible for juvenile hormone transport in the hemolymph of this insect. The juvenile hormone binding protein has been purified using gel filtration, ion exchange chromatography and preparative polyacrylamide gel electrophoresis. The protein is a single polypeptide chain of about 28,000 daltons with a sedimentation coefficient of 2.2S and an isoelectric point of 5.0. Binding analysis using a hydroxyapatite batch assay indicates that the juvenile hormone binding protein has one binding site with a Ka of 1.2 times 10(7) M-1 at 4 degrees C.