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PubMed1995

Mutations in gld-1, a female germ cell-specific tumor suppressor gene in Caenorhabditis elegans, affect a conserved domain also found in Src-associated protein Sam68.

The gld-1 gene of Caenorhabditis elegans is a germ-line-specific tumor suppressor gene that is essential for oogenesis. We have cloned the gld-1 gene and find that it encodes two proteins that differ by 3 amino acids. The predicted proteins contain a approximately 170-amino-acid region that we term the GSG domain (GRP33/Sam68/GLD-1), on the basis of significant similarity between GLD-1, GRP33 from shrimp, and the Src-associated protein Sam68 from mouse (also described as GAPap62 from humans). A conserved structural motif called the KH domain is found within the larger GSG domain, suggesting a biochemical function for GLD-1 protein in binding RNA. The importance of the GSG domain to the function of gld-1 in vivo is revealed by mutations that affect 5 different conserved GSG domain residues. These include missense mutations in an absolutely conserved residue of the KH domain that eliminate the tumor suppressor function of gld-1.

Amino Acid Sequence↗
PubMed1995

Similarities between trunk and spätzle, putative extracellular ligands specifying body pattern in Drosophila.

The basic body plan of Drosophila is specified by four determinant systems that organize pattern along the anteroposterior and dorsoventral axes. Two of these systems (anterior and posterior) depend on localized mRNAs. In contrast, the other two (ventral and terminal) require locally generated extracellular ligands that are transduced, respectively, by the transmembrane receptors Toll and torso (tor). The ligand for the Toll receptor is thought to be spätzle (spz), a secreted protein that is activated by proteolytic cleavage. Here we report that trunk (trk), a gene required for activity of the tor receptor, encodes a protein that resembles spz in several respects. In particular, the sequence suggests that trk is a secreted protein and that it contains an internal site for proteolytic cleavage. Furthermore, the carboxy-terminal domain of trk has a similar arrangement of cysteines to that of spz. We propose that trk encodes an extracellular ligand involved in specifying terminal body pattern and suggest by analogy with spz that a cleaved form of trk constitutes the ligand for the tor receptor.

Alleles↗
PubMed1995

Targeted disruption of mammalian hairy and Enhancer of split homolog-1 (HES-1) leads to up-regulation of neural helix-loop-helix factors, premature neurogenesis, and severe neural tube defects.

Mammalian hairy and Enhancer of split homolog-1 (HES-1) encodes a helix-loop-helix (HLH) factor that is thought to act as a negative regulator of neurogenesis. To directly investigate the functions of HES-1 in mammalian embryogenesis, we performed a targeted disruption of the HES-1 locus. Mice homozygous for the mutation exhibited severe neurulation defects and died during gestation or just after birth. In the developing brain of HES-1-null embryos, expression of the neural differentiation factor Mash-1 and other neural HLH factors was up-regulated and postmitotic neurons appeared prematurely. These results suggest that HES-1 normally controls the proper timing of neurogenesis and regulates neural tube morphogenesis.

Animals↗
PubMed1993

Polymorphic cDNAs encode for the methionine-rich storage protein from Manduca sexta.

By cDNA cloning and sequencing we have shown that Manduca sexta larvae produce three very closely related methionine-rich storage proteins, MMR1, MMR2 and MMR3. Out of 2256 nucleotides in the coding region, the cDNAs differ by at most twenty-one bases and this leads to a single amino acid difference between MMR1 and MMR2, and between MMR2 and MMR3, whereas MMR1 and MMR3 differ by two amino acids. Using both distance and parsimony methods, similarities between the M. sexta and Bombyx mori methionine-rich and arylphorin storage proteins were examined. Homologous proteins from the two species tend to be more closely related than are the two classes of storage proteins in a single species.

Amino Acid Sequence↗
PubMed1996

Differential induction of antibacterial transcripts in Drosophila susceptible and resistant to parasitism by Leptopilina boulardi.

Two well-described elements of the immune response of insects include encapsulation of metazoan parasites (blood-cell-mediated) and the production of antibacterial peptides (humoral and/or cellular). However, the possible functional interrelationship between cellular encapsulation and antibacterial responses, and the extent to which the two components may be co-regulated, are poorly understood. We used a novel approach involving strains of Drosophila resistant (R) or susceptible (S) to the wasp parasitoid Leptopilina boulardi to study the expression of three genes involved in the antibacterial response: Dorsal-related immunity factor (Dif), Cecropin (CecA1) and Diptericin (Dip). Both S and R strains produced high levels of all antibacterial transcripts upon bacterial injection. However, when parasitized the R strain showed no induction whilst the S strain did. This lack of antibacterial transcript induction in the parasitized R strain not only clarifies the separation of these two types of immune response but also raises the fascinating possibility of a link in their genetic regulation.

Animals↗
PubMed1989

A common cytolytic region in myotoxins, hemolysins, cardiotoxins and antibacterial peptides.

Several proteins and polypeptides of reptilian, amphibian, insect, and microbial origin share a common cytolytic property. However, these cytolysins fulfill different objectives. They provide offensive armament in the case of toxins, but defensive systems in the case of antibacterial peptides. The sequences of several nonenzymatic cytolysins and their analogues were compared to identify the structural requirements for cytolytic activity. These cytolysins, although isolated from phylogenetically unrelated organisms, possess the common sequence features of a cationic site flanked by a hydrophobic surface. The presence of such a region apparently confers the cytolytic activity of various cytolysins. The concept of a cytolytic region is strongly supported by the existence of several natural and synthetic analogues of cytolysins and by chemical modification studies of these cytolysins. This prediction provides a new focus for cytolysin research. The understanding of this structure-function relationship should facilitate the design, synthesis, and development of better antibacterial and anticancer peptides.

Amino Acid Sequence↗
PubMed1994

Hydrolysis pattern of procasomorphin by gut proteases from plant parasite Heliothis zea, determined by sequence analyses performed on the unfractionated digestion mixtures.

The digestion pattern of procasomorphin, a putative precursor of beta-casomorphins (beta-casein-derived opioid peptides), by gut proteases from the plant parasite insect Heliothis zea has been determined to evaluate the possibility of introducing in plants the gene encoding for this peptide in order to confer resistance to damage by the insect. The method we used is based on the possibility of deducing the sequence of the fragments produced by proteases at different times of digestion by means of automatic Edman degradation performed on the fragment mixtures without any purification steps. This approach can be considered of general utility in studying the digestion of peptides by a mixture of proteases.

Amino Acid Sequence↗
PubMed1982

Insect immunity: isolation and structure of cecropin D and four minor antibacterial components from Cecropia pupae.

We have investigated low molecular weight antibacterial proteins from the Cecropia moth. Hyalophora cecropia. In addition to the previously described cecropins A and B, five new antibacterial proteins were discovered, the cecropins C, D, E and F, and the factor G. A scheme for the purification of these factors is presented. Cecropin D is a major cecropin, its amino acid sequence, WNPFKELEKVGQRVRDAVISAGPAVATVAQATALAK, shows homology to cecropin A and B. Like these cecropins, cecropin D has a block C-terminal. The previously tentative C-terminal sequence of cecropin A is also confirmed. It is concluded that the three major cecropins, A, B and D, are products of three different genes that are derived from a common ancestor. The cecropins C, E and F were present in very low amounts, and thus their primary structures could not be fully elucidated. Cecropin C has an amino acid sequence that up to residue 37 is identical to the sequence of A, though it lacks the C-terminal blocking group. It may be a precursor or degradation product of cecropin A. The minor cecropin E shows a similar relation to cecropin D. Cecropin F has a single amino acid replacement (17 Asp leads to Asn) compared to cecropin D, and is probably a product of an allele that is present at a low frequency in the population. The primary structure of the factor G could not be determined, however its amino acid composition is different from that of the cecropins. All the major cecropins were found to be efficient against several gram-positive and gram-negative bacterial strains. No significant difference was found between them in their activity against Escherichia coli, though against some less susceptible bacteria the most basic cecropins were more effective, the activity falling in the series B greater than A much greater than D.

Amino Acids↗
PubMed1982

Insect immunity: isolation and structure of cecropins B and D from pupae of the Chinese oak silk moth, Antheraea pernyi.

The immune system in the Chinese oak silk moth, Antheraea pernyi, has been compared with that of the Cecropia moth which has been characterized earlier. Antibacterial activity against Escherichia coli was induced in diapausing pupae by injection of viable E. coli or Enterobacter cloacae. The activity reached a maximum on day 7-8 after which the response gradually declined. The pupae produced a set of immune proteins with P4 and P5 as major labelled components similar to that earlier found in Cecropia. The major antibacterial factor in A. pernyi was cecropin D. A procedure is described for the isolation of cecropin B and D, which is in principle similar to the one used for the isolation of the corresponding cecropins from Cecropia pupae. Amino acid sequence analyses of the A. pernyi cecropins show the D form to contain 36 amino acid residues and that both cecropins have blocked C-termini. The general structure of cecropins having a charged N-terminal region (residues 1-21) followed by a long hydrophobic stretch (residues 22-32) is well conserved. Cecropin B and D from A. pernyi differ from the corresponding proteins in Cecropia by four and three conservative amino acid replacements, respectively. The homology between the cecropins from the two insects suggests that they orginate from a single ancestral gene. The antibacterial activity was tested against nine different bacterial species. Evolutionary aspects of the cecropins are discussed.

Amino Acids↗
PubMed1984

Characterization of inhibitor A, a protease from Bacillus thuringiensis which degrades attacins and cecropins, two classes of antibacterial proteins in insects.

The insect pathogen Bacillus thuringiensis produces an exoprotease, inhibitor A, at the beginning of the stationary growth phase. In vitro, the enzyme selectively destroys cecropins and attacins, two antibacterial proteins found in immune hemolymph from Hyalophora cecropia. The specificity of this enzyme was investigated using cecropin A(1-33) and HPLC for separation and characterization of the fragments obtained. A maximum of 12 different peptides were produced and their positions in the known sequence of cecropin A(1-33) were deduced from their amino acid compositions. The enzyme did not show a stringent requirement for a specific amino acid sequence at the cleavage site but prefers a hydrophobic residue on the C-terminal side. The specificity of the enzyme is explained in terms of the open structure of the cecropins and a pronounced inability of inhibitor A to attack globular proteins.

Amino Acids↗
PubMed1988

Insect immunity. Purification and characterization of a family of novel inducible antibacterial proteins from immunized larvae of the dipteran Phormia terranovae and complete amino-acid sequence of the predominant member, diptericin A.

Injury or injection of live bacteria into third instar larvae of the dipteran insect Phormia terranovae results in the appearance in the haemolymph of at least five groups of heat-stable, more or less basic peptides with antibacterial activity against Escherichia coli. Three of these peptides have been purified. The amino acid sequence has been completely established for one of these and partially (first 40 residues from the N-terminus) for the two others. The sequences show marked homologies indicating that the three peptides belong to a common family. They are not related to other known antibacterial peptides from insects [lysozymes, cecropins (including sarcotoxin I) and attacins]. We propose the name of diptericins for this new family of antibiotic molecules.

Amino Acid Sequence↗
PubMed1988

The structure of the gene for cecropin B, an antibacterial immune protein from Hyalophora cecropia.

Pupae of the moth Hyalophora cecropia respond to an injection of live bacteria by the production of a potent antibacterial activity. The broad-spectrum property of this activity is due chiefly to two small proteins, cecropins A and B. Sequences of the proteins showed them to be homologous and to contain 37 and 35 amino acid residues respectively. The subsequent isolation of two cDNA clones for cecropin B showed that this protein is made as a prepro molecule composed of 62 amino acid residues. We have now prepared a genomic bank and studied four genomic clones for cecropin B. The coding regions were found in two neighbouring BglII fragments, one 0.79 kb and another varying in size from 3.1 kb to 4.9 kb for different clones. One transcriptional unit for preprocecropin B was sequenced and found to be 1035 bp long with a single intron, 514 bp in size. A conserved, insect specific cap site, ATCATTC, was identified by S1 mapping and primer extension experiments. Indications were found for the presence of multigene families and multicopy genes.

Animals↗
PubMed1989

Insect immunity. Isolation of cDNA clones corresponding to diptericin, an inducible antibacterial peptide from Phormia terranovae (Diptera). Transcriptional profiles during immunization.

We have previously isolated and characterized a family of novel 8-kDa cationic antibacterial peptides synthesized by larvae of Phormia terranovae (Diptera) in response to various injuries. These molecules have been named diptericins. The peptide sequence of diptericin A was used to prepare oligonucleotides for screening cDNA libraries and we report in the present paper the isolation of several cDNA clones encoding diptericin. The analysis of the nucleotide sequences indicates that diptericin is synthesized as a prepeptide which is matured in two steps: (a) cleavage of a signal peptide and (b) amidation of the C-terminal residue. Interestingly, the 3' untranslated region of the mRNA contains a consensus sequence TTATTTAT which is also observed in the mRNA of another insect antibacterial peptide (attacin-related sarcotoxin IIA) and in mRNAs encoding proteins related to the inflammatory response in mammals. Our data illustrate that diptericins form a polymorphic family of immune peptides. The transcription of the diptericin genes is rapidly induced in the fat body after inoculation of bacteria, as evidenced by the transcriptional profile.

Amino Acid Sequence↗
PubMed1990

Structure of preproattacin and its processing in insect cells infected with a recombinant baculovirus.

From a cDNA library made from fatbody of immunized Hyalophora cecropia pupae, a full-length clone corresponding to basic attacin was isolated. The corresponding amino acid sequence suggests that basic attacin is synthesized as a 233-residue preproprotein. This was confirmed by cloning the cDNA fragment encoding the basic attacin in the baculovirus Autographa californica nuclear polyhedrosis virus downstream of the polyhedrin promoter and expressing the protein in Spodoptera frugiperda (Sf9) cells. Biologically active attacin was also produced in last instar larvae of Trichoplusia ni after injection of recombinant virus. The concentration obtained was 300-500 times that obtained in cell culture supernatants. In cell culture the induction kinetics of attacin were followed at both transcriptional and translational levels. From the protein processing pattern it was suggested that a protease produced by the Spodoptera cells cleaves attacin at the double arginine residues at positions 45 and 46. The instability of the attacin proteins is rationalized in terms of their random-coil structure which was deduced from circular dichroism measurements.

Amino Acid Sequence↗
PubMed1991

Structure and expression of the attacin genes in Hyalophora cecropia.

To study the regulation of the immune genes in insects, we have cloned and sequenced the attacin gene locus of the giant silk moth Hyalophora cecropia. The locus contains one acidic and one basic attacin gene as well as two pseudogenes, which are remnants of basic attacin genes. A small insertion element was found within the locus. The two functional attacin genes are transcribed in opposite directions and have two introns inserted at homologous positions. A common sequence, GGGGATTCCT, is found at nucleotide position -48 in the acidic gene and at nucleotide position -58 in the basic gene. Interestingly, this decanucleotide is similar to the consensus of the NF-k B-binding site. Expression studies revealed that both attacins are strongly induced by phorbol 12-myristate 13-acetate, lipopolysaccharide and bacteria. However, only the acidic attacin gene showed a clear response to injury.

Animals↗
PubMed1991

Expression of post-translational processing of preprocecropin A using a baculovirus vector.

A cDNA fragment encoding preprocecropin A was inserted into the baculovirus Autographa californica nuclear polyhedrosis virus downstream of the polyhedrin promoter. The gene was expressed in recombinant-infected last instar larvae of Trichoplusia ni and in diapausing pupae of Hyalophora cecropia. The identity of the recombinant product was established by electrophoresis with detection of antibacterial activity and mass spectrometry. The prepropeptide had been correctly processed including removal of signal peptide and pro-part. Biologically active and amidated cecropin A was exported to the hemolymph. The yield of recombinant protein in H. cecropia reached a level of 600 micrograms/ml hemolymph and about 70% of the material was amidated.

Animals↗
PubMed1991

A novel mechanism of Sarcophaga lectin gene expression. Possible involvement of oxidation of the sulfhydryl group of a fat-body protein.

The Sarcophaga lectin gene, an acute-phase-responsive protein of Sarcophaga, was found to be activated when the fat body was incubated in phosphate-buffered insect saline (10 mM NaH2PO4/Na2HPO4, pH 6.2, 2 mM NaHCO3, 1 mM MgCl2, 5 mM KCl, 1 mM CaCl2 and 120 mM NaCl). This activation was selectively suppressed by addition of 2-mercaptoethanol. 2-Mercaptoethanol did not affect the transcription directly, suggesting that the oxidation of the sulfhydryl group of a fat-body protein is required for activation of the Sarcophaga lectin gene. This oxidation reaction seemed to occur immediately when the fat body was incubated in vitro, and once this reaction was initiated, 2-mercaptoethanol no longer inhibited transcription of the Sarcophaga lectin gene. This gene is known to be activated when the larval-body wall of Sarcophaga is injured. It is suggested that the Sarcophaga lectin gene is activated via this novel mechanism on its acute-phase expression in vivo.

Animals↗