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 epiderm is of Manduca sexta larvae was purified by using the photoaffinity ana log for JH II ([H-3]epoxyhomofarnesyldiazoacetate) and partially seque nced. A 1.1-kb cDNA was isolated by using degenerate oligonucleotide p rimers for PCR based on these sequences. The cDNA encoded a 262-amino acid protein that showed no similarity with other known proteins, exce pt for short stretches of the interphotoreceptor retinoid-binding prot ein, rhodopsin, and human nuclear protein p68. Recombinant baculovirus containing this cDNA made a 29-kDa protein that was covalently modifi ed by [H-3]epoxyhomofarnesyldiazoacetate and specifically bound the na tural enantiomer of JH I (K-d = 10.7 nM). This binding was inhibited b y the natural JHs but not by methoprene. Immunocytochemical analysis s howed localization of this 29-kDa protein to epidermal nuclei. Both mR NA and protein are present during the intermolt periods; during the la rval molt, the mRNA disappears but the protein persists. Later when ce lls become pupally committed, both the mRNA and protein disappear with a transient reappearance near pupal ecdysis. The properties of this p rotein are consistent with its being the receptor necessary for the an timetamorphic effects of JH.