Rapid purification and N-terminal amino acid sequence of a photoaffinity-labeled juvenile hormone binding protein from an arctiid moth larva, Platyprepia virginalis

Partial purification of a farnesyl diphosphate synthase from whole-body Manduca sexta

Farnesyl diphosphate synthase (FPP synthase) is a ubiquitous enzyme that is required for the biosynthesis of sesquiterpenes, dolichols ubiquinones, and prenylated proteins in insects. We report on the partial purification and characterization of an FPP synthase, obtained from whole-body preparations of the lepidopteran insect, Manduca sexta. The larval enzyme was separated from isopentenyl diphosphate (IPP) isomerase, phosphatase, and GGPP synthase by preparative isoelectric focusing, and was further purified by DEAE Sepharose, hydroxyapatite, and size exclusion chromatography. Whole-body M. sexta FPP synthase has a native molecular weight of 60.5+/-3.5 kDa and consists of two subunits of 28.5+/-0.5 kDa. As seen with other prenyltransferases, the enzyme has an absolute requirement for divalent cation and both Mn(2+) and Mg(2+) stimulated activity, although the former was inhibitory at higher concentrations. Insect FPP synthase catalyzes the condensation of IPP (K(m)=2.9+/-1.2 microM) with both dimethylallyl diphosphate and geranyl diphosphate (K(m)=0.8+/-0.4 microM). The enzyme requires the presence of detergent, glycerol, and non-specific protein-protein interactions for stability and maximum catalytic activity.

UV-difference and CD spectroscopy studies on juvenile hormone binding to its carrier protein

Juvenile hormone binding protein (JHBP) from hemolymph of Galleria mellonella is a single-chain glycoprotein of molecular mass near 25,880 containing no Trp residues. The fourth derivative of the protein absorption spectrum shows the characteristic vibrational components of the phenylalanine spectrum within the range 240-270 nm. At longer wavelengths two main bands 0-0 and 0+800 cm(-1) appear, caused by vibrational levels of electronic transition, pi-->pi*, in the tyrosine residues, with maxima at 279 nm and 286 nm, respectively. Two intersection points of the second derivative absorption band with abscissa at about 288.8 nm and 283 nm were analysed for estimation of the environment polarity of Tyr residues in the JHBP molecule. The results obtained suggest that JHBP contains at least two classes of Tyr residues with very apolar environment, similar to that found in azurine. In the JHBP-JH complex only one class of Tyr residues located in a very apolar environment was found, and a small perturbation of disulphide bridges was deduced from the UV-difference spectrum. Ligand perturbation appears as a minimum at 243 nm of the UV-difference spectrum. Comparison of the circular dichroism (CD) spectra for free JHBP with the CD spectra for the JHBP-JH complex monitored in the far-UV (190-240 nm) region indicates rather small differences in the secondary structure of the protein. Although ligand binding induces distinct changes in the near-UV (250-300 nm) region of the CD spectrum of JHBP, it is apparent where both Tyr and Phe residues contribute.

Evidence for glycosylation of the juvenile-hormone-binding protein from Galleria mellonella hemolymph

The juvenile-hormone-binding protein (JHBP) from Galleria mellonella hemolymph, which is a member of the high-affinity/low-molecular-mass group of JHBP proteins, was found to be glycosylated. Glycosylation was confirmed by the following evidence. Carbohydrate gas-liquid chromatography analysis of the purified JHBP preparations showed the presence of a low amount of sugars (Man and GlcNAc were the major components). The JHBP electrophoretic band blotted onto nitrocellulose was stained with GlycoTrack (a reagent kit used for the detection of protein glycosylation) and showed strong binding of concanavalin A (ConA). JHBP was fractionated on a ConA-Sepharose 4B column into ConA-bound (strongly stained with ConA) and ConA-unbound (hardly stained with ConA) portions. Both fractions showed juvenile-hormone-binding activity and were glycosylated, as revealed by staining both of them with GlycoTrack. Electrospray-ionization mass spectrometry of JHBP suggested the presence of a small amount of presumably nonglycosylated protein (24988 Da) and five glycoforms, two of which (containing Man2GlcNAc, or Man2Fuc1GlcNAc2 chain) were not bound or were weakly bound to ConA, and three (with Man3GlcNAc2, Man5Fuc1GlcNAc2, or Man5GlcNAc2, chain) were present in the fraction strongly bound to ConA. In conclusion, the monosugar composition, GlycoTrack staining, ConA-binding properties and molecular mass analyses of JHBP supplied convincing evidence for its glycosylation and some information on the character of the oligosaccharide chains.

Key disulfide bonds in an insect hormone binding protein: cDNA cloning of a juvenile hormone binding protein of Heliothis virescens and ligand binding by native and mutant forms

The hemolymph juvenile hormone binding protein (JHBP) from the early fifth instar larvae of Heliothis virescens (Lepidoptera, Noctuidae) has been purified, and three cDNA clones for this protein have been isolated from a fat body cDNA library constructed in bacteriophage lambda ZAP XR. The deduced amino acid sequence of the full-length clone predicts a mature protein consisting of 224 residues, a molecular mass of 24,976 Da, and a pI of 5.29. Comparison of the amino acid sequence to that of the previously described JHBP from Manduca sexta shows 51% overall identity with highly conserved N- and C-terminal regions. One of the three clones bound photoactivatable analogs of juvenile hormones with much lower affinity than the other two. This clone had Phe150 in place of the expected Cys150 conserved in other JHBP clones. The F150C mutant of this clone regained native binding affinity. For native Hvir-JHBP, the affinity for [3H]JH I was lower under reducing conditions (87 nM) relative to a 40 nM affinity under nonreducing conditions. The importance of pairs of Cys residues was addressed by preparing Cys to Ala mutants at each site. Expressed proteins were tested for binding affinity by photoaffinity labeling with tritium-labeled JH analogs and by binding assays using (10R,11S)-[3H]JH I. Curiously, the C150A mutant retained full activity, implying that the aberrant C150F was dysfunctional due to steric hindrance rather than to a missing disulfide linkage. Likewise, C29A and C194A had binding affinities unchanged from that of the full-length wild-type clone.(ABSTRACT TRUNCATED AT 250 WORDS)

Purification and characterization of a juvenile hormone binding protein from hemolymph of the silkworm, Bombyx mori

A juvenile hormone binding protein (JHBP) has been isolated from Bombyx mori hemolymph by gel filtration, ion-exchange chromatography, chromatofocusing and hydroxyapatite column chromatography. Gel electrophoresis indicates that the isolated protein is homogeneous in the presence or absence of a denaturing agent. The JHBP in question has a relative molecular mass of 32 kDa, determined by denaturing gel electrophoresis. Chromatofocusing analysis indicated that the JHBP is an acidic protein with pI 4.9. The protein exhibits a dissociation constant of 9.0 x 10(-8) M for JH I, 1.14 x 10(-7) M for JH II and 3.9 x 10(-7) M for JH III, and thus its affinity for JH analogues is in the order of JH I > JH II > JH III. Its amino acid composition indicates that the protein consists of 297 residues of 18 kinds of amino acids. The sequence of the N-terminus of the polypeptide chain was determined for 34 of the first 36 residues: Asp-Gln-Asp-Ala-Leu-Leu- Lys-Pro-?-Lys-Leu-Gly-Asp-Met-Gln-Ser-Leu-Ser-Ser-Ala-Thr-Gln-Gln-Phe-Le u-Glu- Lys-Thr-Ser-Lys-Gly-Ile-Pro-?-Tyr-His-.

Larva lights: a decade of photoaffinity labeling with juvenile hormone analogues

The introduction of photoaffinity labeling into the mode of action of insect hormones and pheromones started 12 yr ago with the photoaffinity labeling of juvenile hormone binding proteins (JHBPs) from cockroaches in the laboratory of the late John K. Koeppe. Applying this technique to Manduca sexta led ultimately to a three-laboratory collaborative project that has begun to dissect the molecular basis for JH transport, metabolism, and nuclear binding and gene activation in Lepidoptera. This review provides (1) a history of the first experiments; (2) an idea of the breadth of the technique in the arthropod classes Insecta, Crustacea, and Arachnida; and (3) evidence for the depth of the technique in unearthing key details about three different types of the molecular action of JH in M. sexta.

Ligand binding by a recombinant insect juvenile hormone binding protein

A cDNA for the hemolymph juvenile hormone binding protein (JHBP) of larval Manduca sexta has been isolated, sequenced, and expressed in an insect cell line. A recombinant baculovirus, containing the JHBP cDNA fused to the p10 promoter of Autographa californica nuclear polyhedrosis virus, was constructed. Insect cells (Sf9) infected with this virus secreted recombinant JHBP (rJHBP) into the medium (> 50 micrograms/mL), and cotranslational removal of an 18 amino acid leader sequence was observed. rJHBP was cross-reactive with an antiserum prepared to the hemolymph JHBP and was specifically labeled by [3H]EHDA, a photoaffinity analog of JH II, demonstrating that rJHBP was an isoform of the previously reported 32-kDa JHBP [Lerro, K. A., & Prestwich, G.D. (1990) J. Biol. Chem. 265, 19800-19806]. rJHBP was purified from insect cell medium to homogeneity by ion-exchange and gel-filtration chromatography. The purified rJHBP had a higher affinity (KD = 11 nM for JH I and KD = 42 nM for JH II) than that reported for crude hemolymph JHBP (KD = 80 nM for JH I). The circular dichroism (CD) spectrum of purified rJHBP indicated 34% alpha-helix and 23% beta-sheet. The CD spectra of rJHBP in the presence and absence of JH II were the same, indicating no change in secondary structure induced by ligand binding. Thus, the rJHBP expressed in insect cells binds JHs and is suitable for structural and functional analysis.