Fructose-1,6-bisphosphate aldolase from Drosophila melanogaster: primary structure analysis, secondary structure prediction, and comparison with vertebrate aldolases

The Transcription of Flight Energy Metabolism Enzymes Declined with Aging While Enzyme Activity Increased in the Long-Distance Migratory Moth, Spodoptera frugiperda

Of all the things that can fly, the flight mechanisms of insects are possibly the least understood. By using RNAseq, we studied the aging-associated gene expression changes in the thorax of Spodoptera frugiperda females. Three possible flight energy metabolism pathways were constructed based on 32 key metabolic enzymes found in S. frugiperda. Differential expression analysis revealed up to 2000 DEGs within old females versus young ones. Expression and GO and KEGG enrichment analyses indicated that most genes and pathways related to energy metabolism and other biological processes, such as transport, redox, longevity and signaling pathway, were downregulated with aging. However, activity assay showed that the activities of all the five tested key enzymes increased with age. The age-associated transcriptional decrease and activity increase in these enzymes suggest that these enzymes are stable. S. frugiperda is a long-distance migrator, and a high activity of enzymes may be important to guarantee a high flight capacity. The activity ratio of GAPDH/HOAD ranged from 0.594 to 0.412, suggesting that lipid is the main fuel of this species, particularly in old individuals. Moreover, the expression of enzymes in the proline oxidation pathway increased with age, suggesting that this energy metabolic pathway also is important for this species or linked to some aging-specific processes. In addition, the expression of immunity- and repair-related genes also increased with age. This study established the overall transcriptome framework of the flight muscle and aging-associated expression change trajectories in an insect for the first time.

Mechanisms of Insecticidal Action of Metarhizium anisopliae on Adult Japanese Pine Sawyer Beetles (Monochamus alternatus)

Pine wilt disease, caused by Bursaphelenchus xylophilus (pine wood nematode), leads to severe environmental and economic damage. Here, we report the results of experiments on the biological control of pine wilt disease through termination of the insect vector of the nematode and the mechanism of the insecticidal action of Metarhizium anisopliae JEF-279 against Monochamus alternatus (Japanese pine sawyer). A combined treatment with a fungal conidia suspension and a fungal protease-containing culture filtrate caused 75.8% mortality of the insect vector. Additionally, the presence of destruxins was confirmed in the dead Japanese pine sawyer adults, and half of the 10 protein spots in proteomic analysis were identified as an actin related to muscle contraction. Based on proteomic and microscopic analyses, the infection cycle of the Japanese pine sawyer by M. anisopliae JEF-279 was inferred to proceed in the following sequence: (1) host adhesion and germination, (2) epicuticle degradation, (3) growth as blastospore, (4) killing by various fungal toxins (insecticidal metabolites), (5) immune response as defense mechanism, and (6) hyphal extrusion and conidiation. Consequently, the combined fungal conidia suspension and protease-containing culture filtrate treatment may be applied as an insecticidal agent, and flaccid paralysis is likely a major mechanism underlying the insecticidal action of M. anisopliae JEF-279 on host insects.

Backbone makes a significant contribution to the electrostatics of alpha/beta-barrel proteins

The electrostatic properties of seven alpha/beta-barrel enzymes selected from different evolutionary families were studied: triose phosphate isomerase, fructose-1,6-bisphosphate aldolase, pyruvate kinase, mandelate racemase, trimethylamine dehydrogenase, glycolate oxidase, and narbonin, a protein without any known enzymatic activity. The backbone of the alpha/beta-barrel has a distinct electrostatic field pattern, which is dipolar along the barrel axis. When the side chains are included in the calculations the general effect is to modulate the electrostatic pattern so that the electrostatic field is generally enhanced and is focused into a specific area near the active site. We use the electrostatic flux through a square surface near the active site to gauge the functionally relevant magnitude of the electrostatic field. The calculations reveal that in six out of the seven cases the backbone itself contributes greater than 45% of the total flux. The substantial electrostatic contribution of the backbone correlates with the known preference of alpha/beta-barrel enzymes for negatively charged substrates.

Transport of immunoglobulin G and its subclasses across the in vitro-perfused human placenta

OBJECTIVE

The transport of immunoglobulin G and its subclasses 1 to 4 was investigated in the in vitro-perfused isolated cotyledon of the human placenta.

STUDY DESIGN

An in vitro system with separate perfusion of the villous capillary system (fetal compartment) and the corresponding intervillous space (maternal compartment) was set up in an isolated cotyledon of human term placenta. After a 2-hour control phase with both compartments perfused in a closed circuit with NCTC-135 tissue culture medium together with Earl's balanced salt solution (2:1), media were exchanged in both circuits and for the experimental phase immunoglobulin G (Sandoglobulin) together with carbon 14-labeled bovine serum albumin (5-10 microCi) was added to the maternal compartment at a concentration of 6 gm/L. During the experimental phase, lasting between 2 and 5 hours, samples were taken from the maternal and fetal compartments every 30 minutes up to 2 hours and every 60 minutes thereafter.

RESULTS

During the control phase immunoglobulin G appeared in the maternal perfusate and reached a plateau at 60 to 80 mg/L, whereas the concentration in the fetal perfusate did not exceed 20 mg/L. A similar pattern of release was observed for hemoglobin, suggesting a washout of remains of blood from the intervillous space and the villous vascular compartment. After addition of immunoglobulin G to the maternal circuit during the first 2 hours in three of four experiments, no change in immunoglobulin G concentration was seen in the fetal circuit, and only in the fourth and fifth hours did the fetal concentration increase to 0.6% of the maternal concentration. In contrast, carbon 14-labeled bovine serum albumin was already detectable in the fetal circuit after 1 hour, but the level remained constant at 0.1% of the maternal concentration. Total immunoglobulin G transfer was estimated at 0.5% of the amount added to the maternal circulation, which was five times higher than total transfer of bovine serum albumin. Transfer was shown for all four subclasses. At the end of the experiment the ratio of immunoglobulin G1 to immunoglobulin G2 in the fetal perfusate was significantly higher than in the maternal perfusate (3.8 vs 1.8), suggesting preferential transfer of immunoglobulin G1.

CONCLUSION

Transfer of all four immunoglobulin G subclasses of a commercially available immunoglobulin G preparation across the human placenta from the maternal to the fetal side was demonstrated by the dual in vitro perfusion system. There is a preferential transfer for immunoglobulin G1.

Detection of water proximity to tryptophan residues in proteins by single photon radioluminescence

We recently developed a single photon radioluminescence (SPR) technique to measure submicroscopic distances in biological samples [Bicknese et al., and Shahrokh et al., Biophys. J., 63 (1992) 1256-1279]. SPR arises from the excitation of a fluorophore by the energy deposited from a slowing beta decay electron. The purpose of this study was to detect 3H2O molecules near tryptophan residues in proteins by tryptophan SPR. To detect small SPR signals, a sample compartment with reflective ellipsoidal optics was constructed, and amplified signals from a cooled photomultiplier were resolved by pulse-height analysis. A Monte Carlo calculation was carried out to quantify the relationship between SPR signal and 3H2O-tryptophan proximity. Measurements of tryptophan SPR were made on aqueous tryptophan; dissolved melittin (containing a single tryptophan); native and denatured aldolase; dissolved aldolase, monellin, and human serum albumin; and the integral membrane proteins CHIP28 (containing a putative aqueous pore) and MIP26 using 3H2O or the aqueous-phase probe 3H-3-O-methylglucose (OMG). After subtraction of a Bremsstrahlung background signal, the SPR signal from aqueous tryptophan (cps.microCi-1 mumol-1 +/- SE) was 8.6 +/- 0.2 with 3H2O and 7.8 +/- 0.3 with 3HOMG (n = 8). With 3H2O as donor, the SPR signal (cps.microCi-1 mumol-1) was 9.0 +/- 0.3 for monomeric melittin in low salt (trytophan exposed) and 4.6 +/- 0.8 (n = 9) for tetrameric melittin in high salt (tryptophans buried away from aqueous solution). The ratio of SPR signal obtained for aldolase under denaturing conditions of 8 M urea (fluorophores exposed) versus non-denaturing buffer (fluorophores buried) was 1.53 +/- 0.07 (n = 6). Ratios of SPR signals normalized to fluorescence intensities for monellin, aldolase, and human serum albumin, relative to that for d-tryptophan, were 1.42, 1.09, and 1.04, indicating that the cross-section for excitation of fluorophores in proteins is greater than that for tryptophan in solution. For the CHIP28 and MIP26 proteins in membranes, the ratio of SPR signal obtained with 3H2O versus 3HOMG was 1.35 +/- 0.13 (CHIP28, n = 5) and 0.99 +/- 0.02 (MIP26). These data are consistent with the existence of an aqueous channel through CHIP28 that excludes small solutes. We conclude that tryptophan radioluminescence in proteins is measurable and provides unique information about the presence of local aqueous compartments.

Sequence similarities in (alpha/beta)8-barrel enzymes revealed by conserved regions of alpha-amylase

The parallel (alpha/beta)8-barrel is a frequently occurring protein-folding motif. Although the arrangement of secondary structural elements along the barrel is very similar in different (alpha/beta)8-barrel enzymes, there is a very low mutual amino acid sequence homology among the enzymes, contributing in part to the hazy view of their evolution. Here an approach to identifying at least the rough of evolutionarily conserved (alpha/beta)8-barrel sequence is presented. Based on the idea that highly conserved sequence regions of a particular enzyme should be more or less conserved in the sequences of the other evolutionary related enzymes, five sequence similarities of ten different (alpha/beta)8-barrel enzymes were revealed, using the five conserved regions of the amino acid sequence of the alpha-amylase (alpha/beta)8-barrel as the templates.

Chloroplast and cytoplasmic enzymes: isolation and sequencing of cDNAs coding for two distinct pea chloroplast aldolases

Two cDNAs which correspond to two very similar Class I aldolases have been isolated from a pea (Pisum sativum L.) cDNA library. With the exception of one codon they match the experimentally determined N-terminal sequence of a pea chloroplast aldolase. The deduced C-terminal sequence of one of these clones is unique among Class I aldolases. The deduced C-terminus of the other is more like the C-terminus of other eucaryotic Class I aldolases. Comparisons of sequence homology suggest that the pea chloroplast isozymes are only marginally more closely related to the anaerobically induced plant aldolases than to aldolases from animals.

Alternate use of divergent forms of an ancient exon in the fructose-1,6-bisphosphate aldolase gene of Drosophila melanogaster

The fructose-1,6-bisphosphate aldolase gene of Drosophila melanogaster contains three divergent copies of an evolutionarily conserved 3' exon. Two mRNAs encoding aldolase contain three exons and differ only in the poly(A) site. The first exon is small and noncoding. The second encodes the first 332 amino acids, which form the catalytic domain, and is homologous to exons 2 through 8 of vertebrates. The third exon encodes the last 29 amino acids, thought to control substrate specificity, and is homologous to vertebrate exon 9. A third mRNA substitutes a different 3' exon (4a) for exon 3 and encodes a protein very similar to aldolase. A fourth mRNA begins at a different promoter and shares the second exon with the aldolase messages. However, two exons, 3a and 4a, together substitute for exon 3. Like exon 4a, exon 3a is homologous to terminal aldolase exons. The exon 3a-4a junction is such that exon 4a would be translated in a frame different from that which would produce a protein with similarity to aldolase. The putative proteins encoded by the third and fourth mRNAs are likely to be aldolases with altered substrate specificities, illustrating alternate use of duplicated and diverged exons as an evolutionary mechanism for adaptation of enzymatic activities.

Alternate use of divergent forms of an ancient exon in the fructose-1,6-bisphosphate aldolase gene of Drosophila melanogaster

The fructose-1,6-bisphosphate aldolase gene of Drosophila melanogaster contains three divergent copies of an evolutionarily conserved 3' exon. Two mRNAs encoding aldolase contain three exons and differ only in the poly(A) site. The first exon is small and noncoding. The second encodes the first 332 amino acids, which form the catalytic domain, and is homologous to exons 2 through 8 of vertebrates. The third exon encodes the last 29 amino acids, thought to control substrate specificity, and is homologous to vertebrate exon 9. A third mRNA substitutes a different 3' exon (4a) for exon 3 and encodes a protein very similar to aldolase. A fourth mRNA begins at a different promoter and shares the second exon with the aldolase messages. However, two exons, 3a and 4a, together substitute for exon 3. Like exon 4a, exon 3a is homologous to terminal aldolase exons. The exon 3a-4a junction is such that exon 4a would be translated in a frame different from that which would produce a protein with similarity to aldolase. The putative proteins encoded by the third and fourth mRNAs are likely to be aldolases with altered substrate specificities, illustrating alternate use of duplicated and diverged exons as an evolutionary mechanism for adaptation of enzymatic activities.

The crystal structure of fructose-1,6-bisphosphate aldolase from Drosophila melanogaster at 2.5 A resolution

The structure of fructose-1,6-bisphosphate aldolase from Drosophila melanogaster has been determined by X-ray diffraction at 2.5 A resolution. The insect enzyme crystallizes in space group P2(1)2(1)2(1) with lattice replacement with rabbit muscle aldolase as a search model has been employed to solve the structure. To improve the initial phases real space averaging, including phase extension from 4.0 to 2.5 A, has been applied. Refinement of the atomic positions by molecular dynamics resulted in a crystallographic R-factor of 0.214. The tertiary structure resembles in most parts that of the vertebrate aldolase from rabbit muscle. Significant differences were found in surface loops and the N- and C-terminal regions of the protein. Here we present the first aldolase structure where the functionally important C-terminal arm is described completely.

Sequencing of peptides and proteins with blocked N-terminal amino acids: N-acetylserine or N-acetylthreonine

Many proteins cannot be directly sequenced by Edman degradation because they have a blocked N-terminal residue. A method is presented for deblocking such proteins when the N-terminal residue is N-acetylserine (which occurs frequently in eukaryotic proteins) or N-acetylthreonine. The method has been applied successfully to the determination of the N-terminal amino acid sequence of human, bovine, and rat parathymosins. Prothymosin alpha and other blocked proteins and peptides were also readily deblocked and sequenced by this procedure. It is proposed that the mechanism of the deblocking reaction involves an acid-catalyzed N----O shift of the acetyl group followed by a beta-elimination.

Molecular cloning, nucleotide sequence and fine-structural analysis of the Corynebacterium glutamicum fda gene: structural comparison of C. glutamicum fructose-1,6-biphosphate aldolase to class I and class II aldolases

The Corynebacterium glutamicum fda gene encoding fructose-1,6-biphosphate (FBP) aldolase has been isolated by complementation of an Escherichia coli mutant. The nucleotide sequence of a 3371 bp chromosomal fragment containing the C. glutamicum fda gene was determined. The N-terminal amino acid sequence of C. glutamicum FBP aldolase identified the correct initiation site for the fda gene, and a molecular weight of 37,092 was predicted for the fda polypeptide. S1 nuclease mapping identified the transcriptional start site, and Northern hybridization analysis indicated that the fda gene encodes a single 1.3 kb transcript. The primary structure of C. glutamicum FBP aldolase shows strong homology to class II FBP aldolases. Conservation of primary structure was observed between class I and class II aldolases, but several residues essential for catalytic activity in class I aldolases were absent from class II aldolases.