Comparison between cuticular proteins from two locust species, Locusta migratoria and Schistocerca gregaria

Regional differences in degree of resilin cross-linking in the desert locust, Schistocerca gregaria

Various cuticular regions from the desert locust, Schistocerca gregaria, were quantitatively analyzed for two cross-linking amino acids, dityrosine and trityrosine, characteristic constituents of the rubberlike cuticular protein, resilin. These amino acids were found in all regions of cuticle investigated, but in widely varying amounts. In fully mature adult locusts the largest amounts of di- and trityrosine were obtained from the prealar arms and wing-hinges, structures possessing long-range elasticity and being involved in energy storage in the flight system. In structures where deformations tend to occur more slowly, such as the clypeo-labral springs and tracheae, di- and trityrosine are less abundant. In sclerotized cuticle from femur and tibia, as well as in cornea and in the highly stretchable intersegmental membranes of mature females, they are only found in trace amounts and are probably unrelated to elasticity. The trityrosine-to-dityrosine ratio in the various cuticular regions vary from nearly equal amounts of the two amino acids to about ten times more dityrosine than trityrosine, indicating that the regions differ in degree of cross-linking; the tracheal wall is the material with the highest trityrosine-to-dityrosine ratio. In some cuticular regions the ratio increases during maturation from newly moulted (teneral) adults to reproductively active locusts; the most pronounced increase was observed for the wing-hinges, and only a small increase was observed for the abdominal tergal plates. In most cuticular regions in fifth instar locust nymphs the contents of di- and trityrosine corresponded to the contents measured for the adult cuticular regions, but only trace amounts of the two amino acids were obtained from the region of the nymphal wing base which corresponds to the wing-hinge containing cuticular region in adult locusts.

Matrix proteins from insect pliable cuticles: are they flexible and easily deformed?

Proteins from pliable cuticle of locusts, Schistocerca gregaria, and silk moth larvae, Hyalophora cecropia, were studied in solution by means of a fluorescent probe, 8-anilinonaphthalene-1-sulphonic acid (ANS), which is much more fluorescent in non-polar media than in polar media. An intense ANS-fluorescence was observed in the presence of the cuticular proteins at pH-values close to their acidic isoelectric points, and the fluorescence decreased markedly when pH was increased to neutrality or when small amounts of denaturants were added. Aggregation and eventual precipitation of both H. cecropia and locust proteins were obtained by addition of neutral salts, and the aggregation was accompanied by an increased ANS-fluorescence intensity. A decreased ANS-fluorescence was observed at salt concentrations too low to cause visible aggregation of the H. cecropia proteins, probably due to weakened electrostatic interactions between chain segments, but such a decrease was not observed for the locust proteins. The changes in intensity of ANS-fluorescence induced by addition of small amounts of denaturants or salts to solutions of the proteins indicate that more hydrophobic residues are exposed to the solvent, when either hydrophobic interactions or electrostatic attractions between chain segments are weakened. The result is a less compact protein structure, where fewer and smaller hydrophobic clusters are available for protecting ANS-molecules from the quenching effects of water. The effects of denaturants on ANS-fluorescence in the presence of the cuticular proteins are different from those observed for globular proteins, such as hen egg albumen, and the differences can be explained by the suggestion that the cuticular proteins do not have a precisely folded and densely packed hydrophobic core comparable to that present in native globular proteins, and that accordingly they do not undergo a process of denaturation corresponding to that of globular proteins. The behaviour of the cuticular proteins resembles that described for unordered, randomly coiled, thermally agitated polymer chains, whose hydrodynamic volumes depend upon the composition of the medium. It is proposed that the major part of the peptide chains of the cuticular proteins are in an unordered, random structure both when the proteins are in solution and when present in the intact cuticle; probably only the chain regions involved in binding the proteins to chitin will have a well-defined spatial organisation.

Studies on proteins in post-ecdysial nymphal cuticle of locust, Locusta migratoria, and cockroach, Blaberus craniifer

Proteins were extracted from the cuticle of mid-instar nymphs of locusts, Locusta migratoria, and cockroaches, Blaberus craniifer. Seven proteins were purified from the locust extract and five from the cockroach extract, and their amino acid sequences were determined. Polyacrylamide gel electrophoresis indicates that the proteins are present only in the post-ecdysially deposited layer of the nymphal cuticles. One of the locust and one of the cockroach nymphal proteins contain a 68-residue motif, the RR-2 sequence, which has been reported for several proteins from the solid cuticles of other insect species. Two of the cockroach proteins contain a 75-residue motif, which is also present in a protein from the larval/pupal cuticle of a beetle, Tenebrio molitor, and in proteins from the exoskeletons of a lobster, Homarus americanus, and a spider, Araneus diadematus. The motif contains a variant of the Rebers-Riddiford consensus sequence, and is called the RR-3 motif. One of the locust and three of the cockroach post-ecdysial proteins contain one or more copies of an 18-residue motif, previously reported in a protein from Bombyx mori pupal cuticle. The nymphal post-ecdysial proteins from both species have features in common with pre-ecdysial proteins (pharate proteins) in cuticles destined to be sclerotised; they show little similarity to the post-ecdysial cuticular proteins from adult locusts or to proteins from soft, pliable cuticles. Possible roles for post-ecdysial cuticular proteins are discussed in relation to the reported structures.

Characterization of cuticular proteins in the red flour beetle, Tribolium castaneum

We are characterizing the cuticular proteins of Tribolium castaneum (Herbst) (Coleoptera:Tenebrionidae) to determine their role in the function of the exoskeleton. Based on qualitative analyses of cuticles, we focused on the sodium dodecyl sulfate (SDS)-extractable proteins. A small-scale cuticle "mini-prep" procedure was devised that yields preparations virtually free of contaminating cellular material compared to hand-dissected preparations, as assessed by fluorescent microscopy using DAPI to stain nuclei. Proteins extracted in 1% SDS from various developmental stages (last larval instar, pupal, adult) were analyzed by one-dimensional denaturing polyacrylamide gel electrophoresis and by two-dimensional gel electrophoresis. The cuticular protein profiles show both similarities and differences among the stages examined. The amino acid composition, glycosylation, and partial amino acid sequence of several abundant cuticular proteins indicate similarity to cuticular proteins of other insects.

Sequence studies on post-ecdysial cuticular proteins from pupae of the yellow mealworm, Tenebrio molitor

Proteins were extracted from the cuticle mid-instar pupae of Tenebrio and purified by column chromatography. The protein pattern obtained by two-dimensional gel-electrophoresis was different from that obtained from pharate pupal cuticle, indicating that Tenebrio during the post-ecdysial pupal deposits cuticular proteins different from those deposited during the preecdysial period. The complete amino acid sequence was determined for four of the urea-extractable proteins from Tenebrio midinstar pupal cuticle. They range from 5.8 to 16.7 kDa in molecular weights and from 5.2 to 7.9 in isoelectric points. Little similarity was observed between the sequenced post-and pre-ecdysial cuticular proteins from Tenebrio pupae. Only one of the sequenced post-ecdysial proteins contains the Ala-Ala-Pro-Ala/Val motif common in proteins from Tenebrio larval/pupal pharate cuticle and from locust pharate cuticle. None of the post-ecdysial proteins contains the conserved hydrophilic sequence regions described for Tenebrio pharate cuticular proteins.

Amino acid sequence studies on endocuticular proteins from the desert locust, Schistocerca gregaria

Seven proteins from the abdominal cuticle of sexually mature locusts, Schistocerca gregaria, have been extracted, purified and sequenced. None of the proteins have been obtained from the pharate adult cuticle of the same species, and they probably represent post-ecdysially deposited endocuticular proteins. All the proteins contain the Rebers-Riddiford consensus sequence commonly found in cuticular proteins. The proteins are all N-terminally blocked by a pyroglutamine residue, and most of them contain one or more N-acetylhexosamine residues, presumably N-acetylgalactosamine (GalNAc), O-linked to either threonine or serine residues. One of the proteins is C-terminally blocked by an amide group. The unglycosylated forms of the proteins have molecular masses in the range from 9 to 20 kDa. The structures of the endocuticular proteins are discussed in relation to the special mechanical properties of locust abdominal cuticle.

Role of cuticle-degrading proteases in the virulence of metarhizium spp. for the desert locust, schistocerca gregaria

The production of the subtilisin proteinase, PR1, and the trypsin-like enzyme, PR2, in liquid cultures of 19 isolates of Metarhizium spp. was investigated. PR1 activity was generally observed 72 h after inoculation whilst PR2 activity was detected in most strains 48 h after inoculation. PR1 was partially purified from each isolate of Metarhizium spp. The ability of this enzyme from each isolate to degrade different types of insect cuticle was investigated. The cuticle types used were Manduca sexta pupal cuticle, adult desert locust (Schistocerca gregaria) wing cuticle, abdominal cuticle, and pharate adult locust abdominal cuticle. These cuticle types differ in their protein composition and degree of sclerotization. PR1 hydrolyzed the locust cuticle to different degrees. The data suggest a hierarchy for the susceptibility to hydrolysis in the order pharate adult abdominal > adult abdominal > wing. There was no significant correlation between the ability of the enzymes to degrade any of the cuticle types and median lethal time of the isolates against the desert locust. However, a correlation was found between the ability of enzymes to hydrolyze different locust cuticles. Such correlations were not apparent to the same extent between M. sexta cuticle and the locust cuticles. These results are discussed in terms of a possible contribution of PR1 to host specificity. Copyright 1998 Academic Press.

Cuticular proteins from the giant cockroach, Blaberus craniifer

The extractable proteins from selected cuticular regions of nymphs and adults of the cockroach, Blaberus craniifer, have been compared by two-dimensional gel-electrophoresis. Only minor differences in protein patterns were observed when nymphal and adult pre-ecdysial cuticles (presumptive exocuticle) were compared, whereas the pattern obtained from nymphal mid-instar cuticle (mainly endocuticle) differed markedly from that obtained from mature adult cuticle. The pattern obtained from nymphal mid-instar cuticle depended upon the specific cuticular region analysed, but the differences within a stage were, to a large extent, quantitative and not qualitative. Seven nymphal endocuticular proteins have been purified to near homogeneity, and the complete amino acid sequence has been determined for three of them. One of the proteins, Bc-NCP1, contains a 16-residue motif repeated three times and containing a disulphide bridge. Protein Bc-NCP2 has a twice repeated motif in common with a pupal protein from Bombyx mori, and Bc-NCP4 contains a twice-repeated sequence of nine residues and is moreover characterized by an unusual high content of valine (22.0%). None of the protein sequences shows significant similarities to the sequences determined for locus endocuticular proteins, except that they all have pyroglutamate as the N-terminal residue.

Amino acid sequence determination of a protein purified from the shell of the shrimp, Pandalus borealis

One of the urea-extractable proteins in the shell of the shrimp Pandalus borealis has been purified, and the complete amino acid sequence has been determined by the combined use of mass spectrometry and Edman degradation of the intact protein as well as of enzymatically derived peptides. Characteristic features of the sequence are discussed and compared to sequences from insect cuticular proteins and other structural proteins.

Characterization of two high molecular weight catechol-containing glycoproteins from pharate pupal cuticle of the tobacco hornworm, Manduca sexta

Two high molecular weight cuticular proteins (MSCP120 and MSCP246) were extracted in acidic guanidine hydrochloride solution from tanning abdominal cuticle of Manduca sexta pharate pupae and purified by size exclusion high performance liquid chromatography. The apparent molecular weights were ca. 120 and 246 kDa as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Both proteins contained high levels of glutamate/glutamine, glycine, serine, alanine and aspartate/asparagine. MSCP120 was enriched in histidine relative to MSCP246, but the reverse was true for valine and proline. Small quantities of beta-alanine and 3,4-dihydroxyphenylalanine (DOPA), as well as other catechols and carbohydrates, also were detected in the hydrolysates. The proteins became radiolabeled when [1-14C]-beta-alanine was injected into pharate pupae, presumably by the formation of adducts with N-beta-alanyldopamine metabolites during sclerotization. Mild acid hydrolysis released N-beta-alanylnorepinephrine and 3,4-dihydroxyphenylketoethanol from both proteins. Strong acid hydrolysis yielded predominantly 3,4-dihydroxyphenylketoethylamine (arterenone), but also DOPA and dopamine. The N-terminal amino acid sequences of the two cuticular proteins were dissimilar, and that of MSCP246 was more hydrophobic than MSCP120. Both of these proteins were glycosylated with glucose, N-acetylglucosamine and traces of N-acetylgalactosamine, and MSCP246 also contained galactose. These structural glycoproteins, which occur in cuticle undergoing sclerotization, apparently react post-translationally with quinonoid tanning agents to yield catecholamine-protein adducts. Small amounts of peptidyl DOPA probably are formed by hydroxylation of tyrosyl residues. Results from this study are consistent with the hypothesis that these catechol-containing glycoproteins participate in cross-linking reactions in M. sexta pupal cuticle during sclerotization.

The primary structure of an endocuticular protein from two locus species, Locusta migratoria and Schistocerca gregaria, determined by a combination of mass spectrometry and automatic Edman degradation

The complete primary structures of two variants of a protein, Abd-5, isolated from the endocuticles of the migratory locust Locusta migratoria and the desert locust Schistocerca gregaria, have been determined. The proteins from the two species are N-terminally blocked with pyroglutamic acid. Their sequences differed only in two positions. Comparison of the sequences to those of other cuticular proteins shows that moderate homologies exist to 11 other cuticular proteins from insects representing four different orders. Amino acid residues in certain positions appear to be strictly conserved.

Primary structure of a 14 kDa basic structural protein (Lm-76) from the cuticle of the migratory locust, Locusta migratoria

The complete amino acid sequence of a 14 kDa structural protein (LM-76) isolated from pharate cuticle of the locust, Locusta migratoria, was determined by Edman degradation of the intact protein and enzymatically derived peptides. Plasma desorption and electrospray mass spectrometry was used as an integrated part of the structure determination. Protein Lm-76 has characteristics similar to proteins previously isolated from the pharate locust. The amino acid composition shows a high content of alanine (32%) and absence of the amino acids Glu, Cys, Met, Phe and Trp. The sequence has a central hydrophilic region surrounded by two hydrophobic regions with 7 repeats of a (Tyr)-Ala-Ala-Pro-Ala/Val motif. The conservation around the prolyl residues within this sequence motif is demonstrated for the hitherto sequenced presumptive exocuticle proteins from L. migratoria. The N-terminal region of protein Lm-76 is enriched in the amino acids Gly, Leu and Tyr located in the conserved sequence NH2-Gly-Tyr-Leu-Gly-Gly-(Tyr)-.

High resolution two-dimensional mapping of tissue-specific polypeptides in the desert locust, Schistocerca gregaria

High resolution two-dimensional gel electrophoresis (2-DE) using immobilized pH gradients was used to map the tissue-specific polypeptides of the desert locust, Schistocerca gregaria. Highly specific comprehensive 2-DE reference maps ("master gels") were developed for the brain, corpus cardiacum, subesophageal ganglion, and hemolymph. The polypeptides were well resolved within the pH 4-7 range in the first dimension and within the 14-94 kDa molecular mass range in the second dimension.

Comparison of black coral skeleton and insect cuticle by a combination of carbon-13 NMR and chemical analyses

Cross-polarization, magic-angle spinning 13C NMR spectra of skeletal components of individual colonies of the New Zealand black coral, Antipathes fiordensis, have a marked similarity to spectra of the sclerotized exoskeleton of the adult tobacco hornworm, Manduca sexta. NMR analysis estimates the organic content of the load-bearing skeletal base of A. fiordensis as 70% protein, 10% chitin, 15% diphenol, and 5% lipid by weight, and that of M. Sexta moth cuticle as 60% protein, 20% chitin, 15% diphenol, and 5% lipid. The younger pinnules or tips of A. fiordensis are less than 3% diphenol by weight. The only diphenols extracted from coral skeleton by hydrochloric acid are 3-(3,4-dihydroxyphenyl)-DL-alanine (DOPA) and 3,4-dihydroxybenzaldehyde (DOBAL), while the predominant diphenols in acid extracts of insect cuticles are N-acyldopamines. More DOPA is found in the base than in the tips of A. fiordensis and it appears to be a peptidyl component of coral skeletal protein. The oxidation of DOPA and DOBAL to quinones may provide mechanical stabilization of the coral skeleton by cross-linking of structural proteins to other proteins or to chitin.

Determination of the covalent structure of an N- and C-terminally blocked glycoprotein from endocuticle of Locusta migratoria. Combined use of plasma desorption mass spectrometry and Edman degradation to study post-translationally modified proteins

The complete structure of protein isolated from endocuticle of sexually mature locusts, Locusta migratoria, has been determined by a combination of automatic Edman degradation and plasma desorption mass spectrometry. The protein is extensively post-translationally modified. The N-terminal is 5-oxoproline (pyroglutamic acid) and the C-terminal proline residue is amidated. Furthermore, the protein is glycosylated by a single N-acetyl-galactosamine residue at one, two or three threonines. The N-terminal sequence was obtained by analysing the N-acetylated N,O-permethylated derivative using plasma desorption mass spectrometry. The position and type of carbohydrate were determined by combining an HPLC-based carbohydrate analysis with the peak pattern of the phenylthiohydantoin derivative in automatic sequencing and with mass information on peptides. The protein has pronounced similarity to cuticular proteins from larvae of diptera and lepidoptera, but only slight resemblance to the previously sequenced locust exocuticular proteins. This indicates a similarity between soft larval cuticles and locust endocuticle, a similarity which may extend to their mechanical properties.

Cuticular proteins from the shrimp, Pandalus borealis

1. The percentages of mineral salts, chitin, and urea-extractable and non-extractable proteins were determined in pieces of cuticle from selected body regions of the shrimp, Pandalus borealis. 2. Two-dimensional gel-electrophoresis of the urea-extractable proteins shows that a large number of different proteins are present. Identical protein patterns are obtained from the various cuticular regions. 3. A fractionation scheme is presented, which is suitable for obtaining the major proteins in quantities sufficient for further characterization. The amino acid compositions are reported for several of the proteins.