STRUCTURE, EXPRESSION AND GENE SEQUENCE OF A JUVENILE-HORMONE ESTERASE-RELATED PROTEIN FROM METAMORPHOSING LARVAE OF TRICHOPLUSIA NI

A carboxylesterase with an encoded molecular size of 61 kDa and a high sequence similarity to juvenile hormone esterase (JHE) has been clone d from cDNA prepared from final instar larvae of Trichoplusia ni. The absence of a recognizable encoded signal peptide suggests that the enz yme, JHER (for JHE-related) may not be secreted, in contrast to JHE. W hen the amino acid sequence of JHE, JHER and other esterases were mapp ed onto the secondary and tertiary structure determined crystallograph ically for acetylcholinesterase, certain structural features for the s ubstrate binding/catalytic site were identified as common only to JHE and JHER. However, several differences between JHE and JHER were ident ified in residues at the binding/catalytic site, suggesting that altho ugh the two enzymes prefer similar natural substrates, these substrate s are not identical. JHER is present as a single-copy gene, transcribe d during the feeding stage of the final stage of the final larval stad ium, but not after metamorphic commitment to the pupal developmental p rogramme. The gene transcribes a single-size message of 2.0 kb. The ge nes for JHER and JHE appear to be physically juxtaposed in the T. Ri g enome. The 5' flanking sequence to the JHER gene possesses some sequen ces in common with the JHE gene, but is also missing some regulatory e lements previously identified in the JHE gene. Sequences conserved bet ween the promoters for the two genes were identified that were differe nt from previously reported regulatory elements of eukaryotic transcri ption factors.