Juvenile Hormone III as a Natural Ligand for Photoaffinity Labelling of JH-Binding Proteins

Insect Haemolymph, Hormone Binding Proteins, Juvenile Hormone, Photoaffinity Labelling, Manduca sexta, Locusta migratoria Juvenile hormone III, i.e. methyl 10,1 l-epoxy-3,7-dimethyl-2£’,6£'-dodecadienoate, was used for photoaffinity labelling of JH-binding proteins. Irradiation of haemolymph from Manduca sexta and Locusta migratoria in the presence of racemic [10-3H]JH-III results in covalent incorporation of up to 3.2% of the radioactivity into an acetone insoluble protein fraction. Resolution of the proteins by HPLC and by SDS-PAGE confirms the presence of radiolabelled JH-binding proteins. Proteins not involved in JH-binding in insect haemolymph are labelled photochemically with lower yields only. Thus, JH-III is a suitable natural ligand for photo­ affinity labelling of high-affinity binding sites. Use of the natural hormone instead of a hormone analog bears the major advantage that the binding with a JH-binding protein will occur at specific sites.