A NUCLEAR JUVENILE HORMONE-BINDING PROTEIN FROM LARVAE OF MANDUCA-SEXTA - A PUTATIVE RECEPTOR FOR THE METAMORPHIC ACTION OF JUVENILE-HORMONE

A 29-kDa nuclear juvenile hormone (JH)binding protein from the epidermis of Manduca sexta larvae was purified by using the photoaffinity analog for JH II ([H-3]epoxyhomofarnesyldiazoacetate) and partially sequenced. A 1.1-kb cDNA was isolated by using degenerate oligonucleotide primers for PCR based on these sequences. The cDNA encoded a 262-amino acid protein that showed no similarity with other known proteins, except for short stretches of the interphotoreceptor retinoid-binding protein, rhodopsin, and human nuclear protein p68. Recombinant baculovirus containing this cDNA made a 29-kDa protein that was covalently modified by [H-3]epoxyhomofarnesyldiazoacetate and specifically bound the natural enantiomer of JH I (K-d = 10.7 nM). This binding was inhibited by the natural JHs but not by methoprene. Immunocytochemical analysis showed localization of this 29-kDa protein to epidermal nuclei. Both mRNA and protein are present during the intermolt periods; during the larval molt, the mRNA disappears but the protein persists. Later when cells become pupally committed, both the mRNA and protein disappear with a transient reappearance near pupal ecdysis. The properties of this protein are consistent with its being the receptor necessary for the antimetamorphic effects of JH.