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PubMed1987

Interaction between liposomes and sarcotoxin IA, a potent antibacterial protein of Sarcophaga peregrina (flesh fly).

The direct interaction between phospholipids and sarcotoxin IA, a potent bactericidal protein of Sarcophaga peregrina, was studied using authentic sarcotoxin IA, its synthetic derivatives, and various liposomes. Results showed that sarcotoxin IA interacted with liposomes constituted from acidic phospholipids, resulting in the release of glucose trapped in these liposomes. The amidated carboxyl-terminal of this protein was found to be important for this interaction. Liposomes constituted from total phospholipids of Escherichia coli became less susceptible to sarcotoxin IA with an increase in their cholesterol content. Since bacterial membranes do not contain cholesterol, this finding may partly explain the selective toxicity of sarcotoxin I to bacteria.

Animals↗
PubMed1987

Purification and characterization of a proline-rich secretory protein that is a precursor to a structural protein of an insect spermatophore.

The spermatophore or sperm sac of Tenebrio molitor (yellow mealworm beetle) is an acellular structure composed mostly of structural proteins, termed spermatophorins. The proteins are derived from the bean-shaped accessory reproductive glands of the male and are assembled into the multilayered structure within the ejaculatory duct. Homogenates of the secretory plug from this gland were used as immunogens for the production of monoclonal antibodies, including one identified as PL 21.1 which recognizes an antigen in the gland and the spermatophore. With the aid of gel filtration and immunoaffinity chromatography with a PL 21.1, we isolated a glandular secretory protein that is a precursor to a spermatophorin with similar electrophoretic mobility. On native polyacrylamide gels, the antigen from gland homogenates has an apparent molecular mass of 370 kDa. On sodium dodecyl sulfate gels, the antigen from the gland and that from the spermatophore have apparent molecular masses of 23 kDa. According to immunoblots of sodium dodecyl sulfate gels, the 23-kDa glandular antigen is organ-specific and adult-specific. By immunocytochemistry with PL 21.1, we found the antigens to be restricted to secretory vesicles of only one cell type in the gland and to a discrete layer in the outer wall of the spermatophore. The 23-kDa secretory antigen is distinguished by being high in glutamic acid/glutamine (15.4%) and in proline (25.2%).

Animals↗
PubMed1985

Primary structure of sarcotoxin I, an antibacterial protein induced in the hemolymph of Sarcophaga peregrina (flesh fly) larvae.

The primary structure of sarcotoxin I, a potent bactericidal protein induced in the hemolymph of larvae of Sarcophaga peregrina (flesh fly), was investigated. Sarcotoxin I was a mixture of three proteins (sarcotoxins IA, IB, and IC) with almost identical primary structures. These proteins were found to consist of 39 amino acid residues and to differ in only 2-3 amino acid residues. The amino-terminal half of the molecules was rich in charged amino acids and was hydrophilic, whereas the carboxyl-terminal half was hydrophobic. It is suggested that the carboxyl-terminal half of sarcotoxin I penetrates into the bacterial membrane and that its amino-terminal half rich in basic amino acid residues interacts with acidic phospholipids in the bacterial membrane, resulting in perturbation of the membrane and loss of viability of the bacteria.

Amino Acid Sequence↗
PubMed1995

Protein disulphide isomerase and a lumenal cyclophilin-type peptidyl prolyl cis-trans isomerase are in transient contact with secretory proteins during late stages of translocation.

The transport of a presecretory protein into the mammalian endoplasmic reticulum can be divided into early translocation events which include specific targeting of the presecretory protein to and insertion into the endoplasmic reticulum membrane and late translocation events, comprising signal sequence cleavage, completion of translocation and folding of the secretory protein into a functional conformation. The microsomal membrane proteins Sec61 alpha p and translocating-chain-associating membrane protein were previously identified as being in close contact with a nascent presecretory protein at an early step of translocation. Here, we investigated whether additional microsomal proteins are in contact with translocating chains during or immediately after transit. This was addressed by crosslinking after release of the nascent chain from Sec61 alpha p. We observed two additional membrane proteins interacting with the nascent precursor in the early stages of translocation and three lumenal proteins interacting with the processed polypeptide chain in the late stages of translocation. One of the lumenal proteins was identified as protein disulphide isomerase by immunoprecipitation. Another of the lumenal proteins was suggested to be a lumenal cyclophilin-type peptidyl prolyl cis-trans isomerase by the effect of cyclosporin A. We propose that molecular chaperones, such as protein disulphide isomerase and cyclophilin may represent two of the lumenal proteins which are involved in completion of translocation.

Amino Acid Isomerases↗
PubMed1995

[Antimicrobial proteins of insect and their clinical application].

We isolated three antimicrobial proteins from the hemolymph of immunized Sarcophaga peregrina (flesh fly) larvae. These are sarcotoxin I, sapecin and antifungal protein (AFP). Sarcotoxin I and sapecin are highly specific for Gram-negative and Gram-positive bacteria, respectively. AFP was found to have fungicidal activity. Primary target for these antimicrobial proteins was assumed to be microbial membrane. We were able to identify a core undecapeptide of sapecin B. We modified this peptide and finally obtained KLKLLLLLKLK-NH2 and its D-enantiomer. These peptides were effective against various bacteria including MRSA. We found that MRSA-infected mine are cured by treating with these peptides.

Animals↗
PubMedDate not supplied

[Immunological similarities between two cerebral substances from Schistocerca gregaria and two neurohormones from Locusta migratoria].

Two neurohormones produced by two distinctive neurosecretory median cells (A1, B) of the protocerebum have been characterized in Locusta migratoria; on with a multiple functions one called neuroparsin and one stimulating the ovarian maturation called lom OMP. Using the specific immunoserum of these two neurohormones in Schistocerca gregaria, we could demonstrate the occurring of molecules related to the neuroparsin and lom OMP of Locusta. Through histology studies of the brain and corpora cardiaca complex, the immunoserum revealed the presence of the two types of these neurosecretory cells suggesting the occurring in Locusta as well as Schistocerca of the same cells releasing molecules immunologically apparented to neuroparsin and lom OMP. The results were confirmed by electrophoretic separation of corpora cardiaca extract under unreduced conditions followed by a transfer on immobilon membrane.

Animals↗
PubMed1995

TRP, a protein essential for inositide-mediated Ca2+ influx is localized adjacent to the calcium stores in Drosophila photoreceptors.

The Drosophila transient receptor potential (trp) gene product (TRP) shows some structural similarity to vertebrate voltage-gated Ca2+ channels. It appears to function as a novel Ca2+ channel responsible for light stimulated, inositol trisphosphate (InsP3)-mediated Ca2+ entry in the fly retina. The subcellular localization of TRP protein was determined in this study using immunohistochemical staining with anti-TRP antibody (MAb83F6). TRP was localized to the base of the microvilli in a region adjacent to the presumed InsP3-sensitive Ca2+ stores. This specific localization was supported by measuring the magnitude of a TRP-dependent inward current that results from spontaneous activation of the light-sensitive channels during whole-cell recordings (the rundown current, RDC). We found that reduction of the microvilli area through genetic dissection with the opsin null mutant, ninaEora, was correlated with a pronounced enhancement of the TRP-dependent inward current relative to wild type, suggesting that the TRP-dependent current was not produced along the length of the microvilli. We suggest that the functional localization of the TRP protein is on the plasma membrane loop found along the base of the rhabdomeric microvillus. Thus, the TRP channel may function in concert with the InsP3-sensitive Ca2+ stores.

Animals↗
PubMed1995

Vasorelaxant and second messenger effects of maxadilan.

Maxadilan is a potent vasodilator isolated from salivary gland extracts of the sand fly. Although cutaneous vasodilatation is probably the most important physiologic effect of maxadilan (i.e., assisting the sand fly in obtaining a blood meal), it also has effects on other vascular beds. In rabbit isolated aorta, recombinant maxadilan exhibited endothelium-independent relaxations with an IC50 of 24 nM for norepinephrine-induced (1 microM) contractions. Synthetic maxadilan had one-third the potency, with a corresponding IC50 of 74 nM for norepinephrine-induced (1 microM) contractions. Pretreatment with a number of receptor and channel blockers, including tetraethylammonium (1 mM), glyburide (1 microM), barium (0.5 mM), indomethacin (10 microM), propranolol (10 microM), cimetidine (10 microM) and nifedipine (10 microM) did not affect maxadilan-induced relaxations. After treatment with maxadilan, contractions recurred very slowly over approximately 40 min. At a concentration of 1 microM, maxadilan induced a 2- to 3-fold increase in cellular cyclic AMP levels. Maxadilan's activity was selective according to vessel type, with maximal activity in rabbit aorta and mesenteric artery and no activity in porcine and bovine coronary arteries. These studies suggest that maxadilan acts by raising the intracellular levels of cyclic AMP in the smooth muscle of selected blood vessels.

Animals↗
PubMedDate not supplied

Preliminary experimental anticancer activity of cecropins.

The cecropins are a group of peptides that were first isolated from the hemolymph of the giant silk moth, Hyalophora cecropia. In preliminary studies, these novel peptides were shown to be active against several bacteria and mammalian lymphomas and leukemias in vitro. The mechanism of action of the cecropins is thought to involve pore formation at the cytoplasmic membrane. The potential anticancer activity of cecropin B, cecropin P1 and Shiva-1 was investigated against a panel of mammalian cell lines in vitro. Cell lines showed a range of sensitivities to cecropin B (IC50 3.2 to > 100 microM), and two cell lines with the multidrug-resistant phenotype were sensitive to the peptide. In vitro cecropin B activity was virtually complete within one hour. Preliminary in vivo studies showed that cecropin B increases the survival time of mice bearing murine ascitic colon adenocarcinoma cells. Future studies will address structure/activity relationships of similar peptides in order to optimize antitumor activity.

Amino Acid Sequence↗
PubMed1993

A Kazal-type inhibitor with thrombin specificity from Rhodnius prolixus.

A thrombin-specific inhibitor with an apparent molecular mass of 11 kDa has been purified from the insect Rhodnius prolixus. Amino-terminal protein sequence analysis allowed the molecular cloning of the corresponding cDNA. The open reading frame codes for a protein of about 103 amino acid residues and displays an internal sequence homology of residues 6-48 with residues 57-101 indicating a two-domain structure. Based on the amino acid sequence the two domains exhibit high homology to protease inhibitors belonging to the Kazal-type family. Model building suggests that the first domain binds to the active site with residue His10 pointing into the specificity pocket. From gel filtration and tight-binding inhibition experiments the inhibitor appears to form 1:1 complexes with thrombin. Periplasma-directed heterologous expression of the rhodniin cDNA in Escherichia coli yields the intact thrombin inhibitor. Natural and recombinant rhodniin both display inhibition constants of about 2 x 10(-13) M.

Amino Acid Sequence↗
PubMed1993

Storage protein uptake in Helicoverpa zea. Purification of the very high density lipoprotein receptor from perivisceral fat body.

In prepupae of the corn earworm, Helicoverpa zea, storage proteins are taken up by perivisceral fat body, a specialized storage tissue. In this study, the receptor protein for one of these storage proteins, a very high density lipoprotein, was identified, extracted, and purified to homogeneity. The very high density lipoprotein receptor is a glycosylated basic protein with a pI of 8.2 and an apparent molecular weight of 80,000. Binding requires the presence of Ca2+ and has a pH optimum of 7.0. Electron micrographs of immunogold labeled sections show that the receptor is located in the plasma membrane of perivisceral fat body. No receptor is detectable in peripheral fat body which does not sequester storage proteins.

Animals↗
PubMed1993

[Genetic analysis of the interaction of mutations in two genes, controlling expression of MDG4].

Transcription of the retrovirus-like mobile element mdg4 (gypsy) in controlled by the protein product of the suppressor of Hairy wing which interacts with the mdg4 enhancer, and by the protein product of the mdg4 modifier which seems to interact with the su(Hw) protein. In the present work, we studied interaction of mod(mdg4) and su(Hw) mutations in phenotypic expression of mutations induced by mdg4 insertion. Different types of inhibitory effect of mdg4 enhancer on transcription of the target gene were detected. Most frequently, the inhibitory depends on the presence of the mod(mdg4) protein. On of the two acidic domains of su(Hw) protein may be removed without changing the effect. Additional removal of the leucine zipper domain strongly reduces the effect. The second type of inhibition depends of or decrease in the concentration of the mod(mdg4) protein. The su(Hw) protein should have both acidic domains in this case. Sometimes, the su(Hw) protein lacking the C-end acidic domain may activate transcription of a target gene, and this effect does not depend on the presence or absence of the mod(mdg4) protein. The effect may be increased by removal of leucine zipper. Binding of the mod(mdg4) protein to the su(Hw) protein does not depend of the C-end acidic domain and leucine zipper.

Animals↗
PubMed1993

Molecular cloning and sequence of a novel ommochrome-binding protein cDNA from an insect, Manduca sexta.

An ommochrome-binding protein (OBP) from the hemolymph of Manduca sexta has recently been purified and characterized. A cDNA clone was isolated from a fifth instar larval cDNA expression library utilizing antiserum against OBP. Northern blot analysis of total fat body RNA detected a transcript of approximately 1.2 kilobases in fifth instar wandering larvae RNA. The complete nucleotide sequence of the 905-base pair cDNA insert was determined by the dideoxy chain termination method. The OBP cDNA encodes a polypeptide of 274 residues with a predicted molecular weight of 30,580 and with one consensus N-linked glycosylation site. Comparison of the NH2-terminal sequence of the mature protein and the cDNA sequence revealed a typical signal peptide of 18 amino acids. In wandering stage larvae, the OBP transcript appeared to be at least 250-fold less abundant than ribosomal RNA.

Amino Acid Sequence↗
PubMed1993

Purification, characterization, and cDNA cloning of an antifungal protein from the hemolymph of Sarcophaga peregrina (flesh fly) larvae.

An antifungal protein (AFP) was purified from the hemolymph of third instar larvae of Sarcophaga peregrina. This protein repressed the growth of Candida albicans in Sabouraud medium in the presence of nitrofurazone. However, in distilled water or saline, AFP alone killed C. albicans. Significant synergism was detected between AFP and sarcotoxin IA, an antibacterial protein of Sarcophaga. The lethal effect of AFP on C. albicans was greatly enhanced by the presence of a small amount of sarcotoxin IA. AFP was shown to bind to C. albicans and cause leakage of a substance(s) with absorbance at 260 nm from the cells. Analysis of its cDNA showed that AFP is a novel histidine-rich protein consisting of 67 amino acid residues.

Amino Acid Sequence↗
PubMed1995

Activity of lytic peptides against intracellular Trypanosoma cruzi amastigotes in vitro and parasitemias in mice.

Three cecropin-like lytic peptides (DC-1, DC-2, and DC-2R) were synthesized with virtually no sequence homology with the natural compound (cecropin B) while retaining the charge distribution, amphipathic, and hydrophobic properties of the natural compound. A fourth analog (alpha-Pi) without these later properties, but a similar molecular weight, was also synthesized as a nonlytic peptide control. The 3 lytic peptides were examined for their ability to kill Trypanosoma cruzi trypomastigotes in vitro, intracellular amastigotes in vitro, and their toxicity to a mammalian cell line. DC-2 at 5 microM and DC-1 and DC-2R at 10 microM were 100% effective in killing T. cruzi trypomastigotes in vitro, suggesting at least a 10-fold increase in lytic activity over previous tested lytic peptide analogues, SB-37 and Shiva-1. When T. cruzi-infected Vero cells were treated with a single or double exposure of low concentrations (2.5 microM) of DC-1, DC-2, and DC-2R there was a significant (P < 0.05) reduction in amastigote numbers/cell when compared to untreated and alpha-Pi-treated T. cruzi-infected cells. Vero cells alone treated with the lytic peptides showed no reduction in number or toxicity. One of the peptides (DC-1) was tested for its toxicity in AJ mice and its ability to reduce parasitemias in T. cruzi-infected AJ mice. No untoward effects were seen in AJ mice injected intravenously with 50 micrograms/mouse daily for 10 days. There was a significant (P < 0.05) reduction in parasitemia and mortality by day 14 postinoculation (from 100% to 0%) in T. cruzi-infected AJ mice given 25 micrograms of DC-1/mouse on days 2, 4, 6, 8, and 10 postinoculation.

Amino Acid Sequence↗