Structure, expression and gene sequence of a juvenile hormone esterase-related protein from metamorphosing larvae of Trichoplusia ni

Abstract

A carboxylesterase with an encoded molecular size of 61 kDa and a high sequence similarity to juvenile hormone esterase (JHE) has been cloned from cDNA prepared from final instar larvae of Trichoplusia ni. The absence of a recognizable encoded signal peptide suggests that the enzyme, JHER (for JHE-related) may not be secreted, in contrast to JHE. When the amino acid sequence of JHE, JHER and other esterases were mapped onto the secondary and tertiary structure determined crystallographically for acetylcholinesterase, certain structural features for the substrate binding/catalytic site were identified as common only to JHE and JHER. However, several differences between JHE and JHER were identified in residues at the binding/catalytic site, suggesting that although the two enzymes prefer similar natural substrates, these substrates are not identical. JHER is present as a single-copy gene, transcribed during the feeding stage of the final stage of the final larval stadium, but not after metamorphic commitment to the pupal developmental programme. The gene transcribes a single-size message of 2.0 kb. The genes for JHER and JHE appear to be physically juxtaposed in the T. ni genome. The 5' flanking sequence to the JHER gene possesses some sequences in common with the JHE gene, but is also missing some regulatory elements previously identified in the JHE gene. Sequences conserved between the promoters for the two genes were identified that were different from previously reported regulatory elements of eukaryotic transcription factors.

Abnormal development in larvae of Sesamia nonagrioides (Lepidoptera: Noctuidae) resulting from baculovirus-mediated overexpression of a JHE-related gene (SnJHER)

“…In this respect the expression of JHER appears similar to that reported for certain other genes that are highly expressed before, but not after, metamorphic commitment, such as the arylphorin gene that is controlled by ecdysteroids (Jones et al, 1994). It is suggested that, TniJHE and TniJHER are physically juxtaposed in T. ni (Jones et al, 1994).…”

“…Moreover, if cells were treated with tunicamycin (a strong inhibitor of N-linked glycosylation), the apparent size of the immunopositive bands decreased to 60 kDa. As is the case for all JHE and JHER proteins studied so far (Jones et al, 1994), SnJHER also contains glycosylation sites [NX(S/T)] in its predicted protein sequence (Kontogiannatos et al, 2011).…”

“…Closely related enzymes, the juvenile hormone esterase related enzymes (JHERs), contain a cysteine residue immediately adjacent to the catalytic serine, in contrast to most other described esterases, including JHE, which have alanine at this position (Jones et al, 1994;Kontogiannatos et al, 2011). In Trichoplusia ni it is proposed that a JH-like compound could be the target of the JHER enzyme (Jones et al, 1994). TniJHER is not induced by the powerful JH analog, fenoxycarb, while it is highly expressed just before the metamorphic commitment to the pupal developmental program and away from the larval program (Jones et al, 1994).…”

“…In Trichoplusia ni it is proposed that a JH-like compound could be the target of the JHER enzyme (Jones et al, 1994). TniJHER is not induced by the powerful JH analog, fenoxycarb, while it is highly expressed just before the metamorphic commitment to the pupal developmental program and away from the larval program (Jones et al, 1994). In this respect the expression of JHER appears similar to that reported for certain other genes that are highly expressed before, but not after, metamorphic commitment, such as the arylphorin gene that is controlled by ecdysteroids (Jones et al, 1994).…”

Regulation of JH titers: The relevance of degradative enzymes and binding proteins

“…The similarities are particularly extensive in the N-terminal halves of the enzymes, and computer analysis also showed that JHE contains a serine active site, common to hydrolases. This information indicates an evolutionary relationship between JHE and other esterases (Hanzlik et al, 1989;Jones et al, 1994), and suggests that carboxylesterases may have evolved by gene amplification and divergence. A better understanding of the phylogenetic relationships of the different esterases will be possible once more information on the primary sequences of JHEs and other esterases becomes available.…”