Synthesis and binding affinity of an iodinated juvenile hormone.
The synthesis of the first iodinated juvenile hormone (JH) in enantiomerically enriched form is reported. This chiral compound, 12-iodo-JH I, has an iodine atom replacing a methyl group of the natural insect juvenile hormone, JH I, which is important in regulating morphogenesis and reproduction in the Lepidoptera. The unlabeled compound shows approximately 10% of the relative binding affinity for the larval hemolymph JH binding protein (JHBP) of Manduca sexta, which specifically binds natural 3H-10R,11S-JH I (labeled at 58 Ci/mmol) with a KD of 8 X 10(-8) M. It is also approximately one-tenth as biologically active as JH I in the black Manduca and epidermal commitment assays. The 12-hydroxy and 12-oxo compounds are poor competitors and are also biologically inactive. The radioiodinated [125I]12-iodo-JH I can be prepared in low yield at greater than 2500 Ci/mmol by nucleophilic displacement using no-carrier-added 125I-labeled sodium iodide in acetone; however, synthesis using sodium iodide carrier to give the approximately 50 Ci/mmol radioiodinated ligand proceeds in higher radiochemical yield with fewer by-products and provides a radioligand which is more readily handled in binding assays. The KD of [125I]12-iodo-JH I was determined for hemolymph JHBP of three insects: M. sexta, 795 nM; Galleria mellonella, 47 nM; Locusta migratoria, 77 nM. The selectivity of 12-iodo-JH I for the 32-kDa JHBP of M. sexta was demonstrated by direct autoradiography of a native polyacrylamide gel electrophoresis gel of larval hemolymph incubated with the radioiodinated ligand. Thus, the in vitro and in vivo activity of 12-iodo-JH I indicate that it can serve as an important new gamma-emitting probe in the search for JH receptor proteins in target tissues.
Prestwich
G D
GD
Department of Chemistry, State University of New York, Stony Brook 11794-3400.
Eng
W S
WS
Robles
S
S
Vogt
R G
RG
Wiśniewski
J R
JR
Wawrzeńczyk
C
C
D000818:Animals; D001667:Binding, Competitive; D002352:Carrier Proteins / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005470:Fluorometry; D006458:Hemolymph / Q000378:metabolism; D019476:Insect Proteins; D007457:Iodine Radioisotopes; D007553:Isotope Labeling; D007700:Kinetics; D007915:Lepidoptera; D012717:Sesquiterpenes / Q000138:chemical synthesis* / Q000378:metabolism; D013237:Stereoisomerism
D002352:Carrier Proteins; D019476:Insect Proteins; D007457:Iodine Radioisotopes; D012717:Sesquiterpenes; C035606:juvenile hormone-binding protein, insect; C008442:juvenile hormone I