The Juvenile Hormone Binding Protein in the Hemolymph of Manduca sexta Johannson (Lepidoptera: Sphingidae).

C(18):juvenile hormone is quite soluble in water, yielding a monomeric solution greater than 10(-5) M. In vivo injection or addition of aqueous juvenile hormone to the hemolymph in vitro shows the complexation of juvenile hormone to a protein, as demonstrated by gel permeation chromatography and disc-gel electrophoresis. The protein has an apparent molecular weight of 3.4 x 10(4) and is present in the hemolymph at a concentration in the micromolar range. The binding of the hormone to the protein can be described as a simple thermodynamic equilibrium with a dissociation constant of 3 x 10(-7) M, and the protein has a much higher affinity for the hormone than for the hydrolysis products.