MICROSOMAL JUVENILE-HORMONE BINDING-PROTEINS IN THE FOLLICLE CELLS OFTENEBRIO-MOLITOR

The microsomal fraction of Tenebrio molitor follicle cells has been fo und to contain both high and low affinity binding sites for juvenile h ormone (JH) III. Using Scatchard analysis, the equilibrium dissociatio n constants, K-d, were calculated as 1.0 x 10(-8) and 4.3 x 10(-7) M r espectively. Kinetic data support a rapid binding of the hormone to th e site(s), with rate constants of k(a) = 3.77 x 10(8) M(-1) min(-1) an d k(d) = 0.0075 min(-1). Affinity of the binding site(s) for JH III wa s higher than for either JH I or methoprene. The significance and poss ible function of such microsomal binding proteins are discussed, with reference to the perturbance of vitellogenesis found in beetles parasi tized by Hymenolepis diminuta.