A cDNA fragment of haemolymph juvenile hormone binding protein (hJHBP) from
larvae of Bombyx mori was amplified by RT-PCR using degenerate primers bas
ed on the N-terminal amino acid sequence of purified hJHBP and a conserved
region near the C-terminus of other lepidopteran hJHBPs. 5'- and 3'-ends we
re amplified by RACE to yield cDNAs, hJHBP1 and hJHBP2, encoding 225 amino
acids with three substitutions. hJHBP-mRNA levels in the fat body were cons
tant in the 4th instar, but decreased in the 5th, JHBP protein was constant
until wandering, then declined. Recombinant hJHBP1 expressed in E. coli mi
grated on SDS-PAGE with a M-r of 32 kDa and showed a K-d of 4.5 x 10(-7) M
with JH III, both similar to those of native hJHBP.