The hemolymph titer of juvenile hormone binding protein and binding sites during the fourth larval instar of Manduca sexta

Abstract

The binding activity of a hemolymph juvenile hormone binding protein has been studied during the fourth instar of Manduca sexta. Multiple equilibrium dialysis as well as immunochemical precipitation suggests that the activity of juvenile hormone binding protein follows the curve for hemolymph protein concentration and not the juvenile hormone titer. Specific increases in binding occur at the time of ecdysis from the third to the fourth larval instar and from the fourth to the fifth larval instar. Estimations of binding sites indicate that early- and late-instar larvae have approximately the same number of sites (1.5 × 10 −7, M) and that the same protein is responsible for binding throughout the instar.