Isolation and characterization of a high molecular weight JH‐III transport protein in the hemolymph of locusta migratoria

The juvenile hormone binding protein in Locusta migratoria is a very high density lipoprotein of Mr ∼ 566,000. It contains 15% lipid and is composed of six seemingly identical subunits of Mr ∼ 77,000. It is a minor protein, constituting 1–2% of the total hemolymph proteins. Its concentration fluctuates with total protein content and follows a cyclic pattern related to the molting cycles. The binding protein has a high affinity for (10R)‐juvenile hormone III. The dissociation constant for the hormone is 3.7 ∼ 0.6 nM, and one binding molecule contains six hormone‐specific binding sites. The concentration of binding sites in the hemolymph is therefore very high, reaching a value of 26 μM in the last larval instar and 11 μM in the adult male.