Characterization of a methyl farnesoate binding protein in hemolymph from Libinia emarginata

Hemolymph from Libinia emarginata was tested for its ability to bind methyl farnesoate (MF), a JH-like compound found in many crustaceans. Hemolymph bound MF with moderate affinity (KD = 4.5 x 10(-6) M). Competitive binding studies showed that this binding was specific for MF, with farnesoic acid and JH homologues having less than 30 and 7%, respectively, of the relative binding activity of MF. JH acid and ecdysterone had no binding activity. MF binding activity was lost after pretreatment of hemolymph with heat or protease, suggesting that the binding component was a protein. Gel filtration analysis showed that the binding activity had a molecular weight of about 650,000.