Production in Escherichia of moricin, a novel type antibacterial peptide from the silkworm, Bombyx mori

Moricin is a novel type antibacterial peptide recently isolated from the silkworm, Bombyx mori. Two foreign gene expression systems in Escherichia coli were employed to obtain a large amount of the peptide for further characterization. An artificial moricin gene was chemically synthesized and inserted into two expression vectors, pXa1 and pMAL-c2. The recombinant moricin was efficiently produced in E. coli as fusion proteins and released by chemical cleavage with cyanogen bromide or o-iodosobenzoic acid. Eleven milligrams of pure recombinant moricin was obtained from 2 L of E. coli culture. The primary structure and molecular mass of the purified recombinant moricin was the same as those of the natural moricin. In addition, the antibacterial activity of the recombinant moricin against E. coli and Staphylococcus aureus was comparable to that of the natural moricin.

Sensitization to reactive textile dyes in patients with contact dermatitis

Reactive dyes are used especially for colouring natural fibres (cotton, silk and wool) that are widely used in Western countries, particularly Italy, in the production of clothes. The aim of our study was to investigate sensitization to the most commonly used reactive textile dyes in patients undergoing patch tests, and to assess the clinical relevance of contact sensitization to these dyes. 1813 consecutive patients underwent patch tests with the GIRDCA standard series and an additional textile series of 12 reactive dyes. 18 of these patients were sensitized to reactive dyes (0.99%) (4 only to reactive dyes). The dyes most frequently responsible for positive patch tests were Red Cibacron CR and Violet Remazol 5R (respectively, 8 and 5 positivities). In 5 cases only was a history of intolerance to particular garments given; of 4 patch tests performed with pieces of garment, 2 were positive. In 1 occupationally-exposed patient, airborne contact dermatitis was suspected. Owing to the lack of up-to-date patch test series, some cases of allergic contact dermatitis from textile dyes are probably misdiagnosed: new colouring agents are continuously introduced to the market, so that a close relationship with textile industry is necessary to improve our diagnostic tools.

An endochitinase gene expressed at high levels in the stylar transmitting tissue of tomatoes

A gene (pMON9617; Chi2;1) identified by screening a tomato pistil cDNA library has been found to encode a protein similar in sequence to class II chitinases. Using a baculovirus expression system we show that the Chi2;1 protein is an active endochitinase. The Chi2;1 protein is most similar in sequence to a previously described stylar chitinase (SK2) isolated from potato. Both proteins lack the diagnostic N-terminal cysteine-rich regions and the C-terminal vacuolar targeting signals of class I chitinases and appear to define a novel type of class II endochitinases associated with flowers. Chi2;1 is expressed predominantly in floral organs and its expression within these organs is temporally regulated. The highest level of expression is found in the transmitting tissue of the style where Chi2;1 mRNA begins to accumulate just prior to anthesis. In vegetative tissue, low levels of Chi2;1 mRNA were detected, and these levels did not increase in response to wounding or treatment with ethephon. mRNA from Chi2;1 orthologs was not detected in most other angiosperms tested, even including some members of the Solanaceae, and it is therefore unlikely that Chi2;1 is essential for stylar function. A fragment containing 1.4 kilobase pairs of 5'-flanking DNA from the Chi2;1 gene was shown to drive high-level expression of an attached reporter gene in the styles of transgenic tomatoes. This fragment has utility for engineering expression of other coding regions in styles.

Cell-free production of the silkworm sex pheromone bombykol

Cell-free production of bombykol was done by incubating a pheromone gland homogenate in the presence of NADPH, ATP, and CoA. Addition of n-hexane to the reaction mixture stimulated bombykol production, resulting in production of 238 ng of bombykol from the homogenate equivalent to 2 pheromone glands after 23 h. Removal of either NADPH, ATP, or CoA resulted in no stimulation of bombykol production, suggesting that the final step of the bombykol biosynthetic pathway is done by acyl CoA synthetase and reductase, sequentially. Incubation first with ATP or high concentrations of ATP suppressed the production of bombykol. Since incubation with ATP also inhibited conversion of [1-14C]palmitoyl CoA into 1-hexadecanol, the inhibitory action of ATP seemed attributable to inactivation of the acyl CoA reductase by phosphorylation, as mediated by a protein kinase in the homogenate. Our results suggest that the activity of acyl CoA reductase in bombykol biosynthesis is regulated by phosphorylation/dephosphorylation, and that the activation occurs by dephosphorylation as mediated by phosphoprotein phosphatase.

Human trehalase: characterization, localization, and its increase in urine by renal proximal tubular damage

By using polymerase chain reaction, cDNA encoding human renal trehalase has been isolated. The partial amino acid sequence deduced by the cDNA showed homologies in rabbit, Tenebrio molitor and silkworm trehalase. Northern blots showed renal trehalase mRNA to be about 2.0 kb. To examine the properties of renal and urinary human trehalase, the trehalase cDNA was inserted in the pMAL-cRI vector downstream from the malE gene, which encodes maltose-binding protein. Transfection of the recombinant pMAL-cRI in Escherichia coli provided high levels of expression of the maltose binding protein-trehalase fusion protein. A rabbit was immunized with purified fusion protein, and antihuman trehalase antibodies were obtained. Immunoblot analysis disclosed that renal and urinary trehalase exhibited a molecular mass of about 75 kDa. Analysis by indirect fluorescent microscopy demonstrated that the enzyme located in only proximal tubular cells. Urinary trehalase activity was low in the healthy infants and elevated in patients with asphyxia. Markedly high activity was observed in a patient with Lowe syndrome. The immunoreactive urinary trehalase with 75 kDa was increased dependent on the elevation of the activity. On the basis of these findings, we conclude that the increase of urinary trehalase reflects the extent of renal tubular damage, and we propose that urinary trehalase can be a specific marker of renal tubular damage.

Western blotting using recombinant Hantaan virus nucleocapsid protein expressed in silkworm as a serological confirmation of hantavirus infection in human sera

Recombinant Hantaan virus nucleocapsid protein expressed in silkworm larvae was applied as a serological diagnostic antigen in Western blots (WB) of human sera. The sensitivity of this method was similar to that of the IFA test. Hemorrhagic fever with renal syndrome (HFRS) and nephropathia epidemica diagnosed by their cross-reactivity in WB. The specificity of this method was higher than that of IFA test because the background was low. Sera that exhibited high background staining in the IFA test were readily diagnosed with this method. We recommended WB using recombinant Hantaan virus nucleocapsid antigen as a confirmatory procedure for the serodiagnosis of hantavirus.

Moricin, a novel type of antibacterial peptide isolated from the silkworm, Bombyx mori

A novel antibacterial peptide that shows antibacterial activity against Staphylococcus aureus was isolated from the hemolymph of the silkworm, Bombyx mori. The novel peptide consisted of 42 amino acids and was highly basic. This peptide indicated no significant similarity with other antibacterial peptides. The peptide showed antibacterial activity against several Gram-negative and -positive bacteria and had a higher activity against Gram-positive bacteria than cecropin B1, a major antibacterial peptide of B. mori. The novel peptide was inducible by bacterial injection. These results suggest that the peptide is responsible for the antibacterial activity in B. mori against Gram-positive bacteria. The effects of the peptide on bacterial and liposomal membranes showed that a target of the peptide is the bacterial cytoplasmic membrane. The results also suggest that the N-terminal portion of the peptide, containing a predicted alpha-helix, is responsible for an increase in the membrane permeability. We propose the name "moricin" for this novel antibacterial peptide isolated from B. mori.

Attachment and growth of cultured fibroblast cells on silk protein matrices

The attachment and growth of L-929 cells on films made of Bombyx mori silk proteins--fibroin and sericin and their mixtures--was studied by a cell culture method. Both cell attachment and growth were dependent on a minimum of around 90% sericin in the mixture. The results from electron micrography as well as from the DSC measurements supported the notion that the mixture of the two proteins fibroin and sericin has a phase-separated structure in the solid state. The observed minimum of sericin in the cell attachment and growth is thought to be a result of this phase-separated structure. Films of pure component proteins (i.e., 100% fibroin or sericin) exhibited as high a cell attachment and growth as collagen, a widely used mammalian cell culture substrate. However, a morphological study of the attached cells revealed that the cells attached to silk fibroin were extended and had a spindle shape, just like the cells attached to collagen, while the cells attached to the silk sericin had a different shape. It is concluded, therefore, that the attachment condition on silk fibroin is ideal for the viability, growth and function of the cells.

Separation of juvenile hormone metabolites with a silica-based gel permeation column

Metabolites of juvenile hormone (JH) III, JH acid, JH diol and JH acid diol in an aqueous solution were separated by gel permeation chromatography using an UltraSpherogel SEC 2000 column. Each metabolite was eluted in an inclusion volume in the order JH acid diol, JH acid and JH diol. Although JH was the last compound eluted, it was co-eluted with a JH-binding protein (JHBP) when JHBP was present in the solution. Using this method, in vivo and in vitro JH catabolism studies were performed in the fifth stadium larvae of Bombyx mori.

20-Hydroxyecdysone stimulates RNA polymerase I activity in silkmoth wing epidermis by increased synthesis and phosphorylation

The activities of RNA polymerases I and II in the wing epidermis of diapausing silkmoth pupae increased about tenfold during the first day after administration of either 20-hydroxyecdysone (20E) or 20E plus juvenile hormone (Katula et al., 1981a). The aim of these studies was to correlate these increases in RNA polymerase I and II activities to their amounts in hormone stimulated wing epidermis. The enzyme activities were measured by standard procedures while their amounts were determined by the application of a modified ELISA with subunit-specific monoclonal antibodies. Results showed that the increase in the amount of RNA polymerase I during the first 24 h accounted for only about 60% of the increase in activity. Alkaline phosphatase decreased the activity of the newly synthesized enzyme by 40-50%. These results indicate that hormone-stimulation of RNA polymerase I activity is due to a combination of synthesis of the enzyme and phosphorylation of the enzyme and/or tightly associated factors. RNA polymerases II and III determined by differential ELISA using a monoclonal antibody specific to a common subunit followed developmental changes similar to those of RNA polymerase I. The amounts and activity of the enzymes during the first 48 h were similar in wing tissue that followed the second pupal development (20E + juvenile hormone) compared to tissue that developed into adult wings (20E).

Attachment and growth of fibroblast cells on silk fibroin

The attachment and growth of fibroblast cells (L-929) on matrices of silk fibroin from Bombyx mori domestic silkworm (DSF) and Antheraea pernyi wild silkworm (WSF) were studied by a cell culture method. The performance of the two kinds of silk fibroin was compared to that of collagen. DSF exhibited as high a cell attachment and growth as collagen did. The cells attached to DSF were extensively spread out and their filopodia were visible in the SEM pictures. WSF, which contains the tripeptide sequence Arg-Gly-Asp (believed to be a specific interaction site for cell-attachment), displayed much higher cell attachment and growth compared to DSF. The cells attached on WSF became virtually flat and their filopodia could be seen, indicating that the cells were very strongly held on the surface.

Distribution and characterization of specific cellular binding proteins for bone morphogenetic protein-2

Bone morphogenetic proteins (BMPs), which were originally identified by their novel ability to induce de novo cartilage and bone formation in vivo, are multifunctional proteins structurally related to transforming growth facto-beta s, activins, and inhibins. As a first step to elucidate the precise physiological function as well as the action mechanism of BMPs, we have examined the distribution of the specific cellular binding proteins for BMP-2 on a wide variety of cell types. A single class of high affinity-specific binding sites for BMP-2 were identified not only on osteoblastic cells but also on major types of non-hematopoietic cells in a rather ubiquitous fashion (1,200-60,000 receptors/cell, Kd = 35-230 pM); these cells included fibroblasts, keratinocytes, astrocytes, kidney epithelial cells, and tumor cells of bone, muscle, lung, liver, kidney, stomach, colon, prostate, and neuronal tissue. Other growth factors including transforming growth factor-beta 1, activin A, and inhibin A did not compete for the binding of 125I-labeled BMP-2 to the cells. Affinity cross-linking of radiolabeled BMP showed five components with apparent molecular masses of 170, 105, 90, 80, and 70 kDa common to all three fibroblast cell lines analyzed. On the other hand, no specific binding sites for BMP-2 were identified on vascular endothelial cells or on hematopoietic cells including RPMI 1788 and RPMI 8226 (B-lymphocyte lineage), MOLT-3 and MOLT-4 (T-lymphocyte lineage), HL-60 (myeloid lineage), and K-562 (erythroid lineage). These results suggest that major types of cells other than hematopoietic cells and vascular endothelial cells may be potential targets for BMP-2 action.

Bacillus thuringiensis protoxin: location of toxic border and requirement of non-toxic domain for high-level in vivo production of active toxin

Insecticidal crystal proteins, or protoxins, of Bacillus thuringiensis are composed of two domains, an amino-terminal half essential for toxicity, and a carboxy-terminal half with an as yet unassigned function. To define the boundary of the two domains, sequential termination codons were introduced from the 3'-end of the DNA sequence encoding the toxic domain of the 1155-residue cry1A(b) gene product. The mutated and the intact genes were placed under the control of the Escherichia coli inducible promoter PrecA, and toxicity of the cell extracts was determined using silkworm larvae. Under non-induced conditions, in which the gene products accumulated to a limited degree, mutations encoding 606 amino acid residues or more were toxic, whereas those encoding 605 residues or less were non-toxic. Comparison of the toxicities and the levels of the toxic proteins suggested that the mutant proteins had comparable activity to that of the intact protoxin. Furthermore, the non-toxic protein seemed to be unstable in the extracts. To investigate the roles of the non-toxic domain, the mutant proteins were overproduced in both E. coli and B. thuringiensis. The intact and the mutated genes carrying natural promoters were introduced into acrystalliferous B. thuringiensis. Upon induction of PrecA in E. coli, and upon sporulation in B. thuringiensis, there was a large accumulation of gene products which formed inclusion bodies. The inclusion bodies of the intact protoxin were active, whereas those of the mutant proteins were inactive. Inclusion bodies of the intact protein could be solubilized in alkali, whereas the mutant inclusion bodies were insoluble. Since solubilization under alkaline conditions in the insect midgut is considered to be the first step of toxic action, the non-toxic domain is required to direct the synthesis of inclusion bodies as an active soluble form.

Cloning and expression of the gene of hemocytin, an insect humoral lectin which is homologous with the mammalian von Willebrand factor

Invertebrate lectins play an important role in a non-specific self-defense mechanism, as invertebrates do not synthesize specific antibodies. We report the cloning of several overlapping cDNAs encoding the entire silkworm (Bombyx mori) lectin, which we propose to call hemocytin. The sequence (10477 bp) encoded 3133 amino acids. The characteristics features of the carbohydrate-recognition domain of C-type animal lectin were revealed at C-terminal sequence of hemocytin. When cDNA encoding this region was introduced into baculovirus vector, hemagglutinating activities were detected in the culture fluid of a recombinant virus-infected cells. These activities were inhibited by D-mannose, N-acetyl-D-galactosamine, and D-maltose which are haptenic saccharides of authentic hemocytin. Analysis of dot and Northern blot hybridization revealed that hemocytin gene was transcribed in hemocytes of the silkworm at larval-pupal metamorphosis and/or after the injection of Escherichia coli and lipopolysaccharide. After silkworm larvae were injected with C-terminal portion of hemocytin, aggregation of hemocytes was observed in the hemolymph. Hemocytin has significant homology with mammalian von Willebrand factor which involves in platelet adhesion to subendothelium. Also, hemocytin has a homologous region with coagulation factor V and VIII. These results suggest that hemocytin molecule is an adhesive protein and relates to hemostasis or encapsulation of foreign substances for self-defense.

Interaction of silkworm larvae expressed monomeric hM-CSF with its receptor on murine bone marrow derived macrophage

Human macrophage colony-stimulating factor (hM-CSF) expressed in the silkworm larvae was monomeric. The nature of the interaction of iodinated monomeric M-CSF with murine bone marrow derived macrophage (BMM) was studied. On incubation with 2 nM [125I]M-CSF at 4 degrees C, approximately 90% of the maximal binding occurred within 15 min with a plateau around 1hr which then gradually declined. Scatchard plot analysis showed that the Kd for the monomeric M-CSF is 5.3 x 10(-10) M and the number of binding sites per cell is 4 x 10(4). Competition experiment indicated that cellular binding of the iodinated monomeric rhM-CSF was almost as effective as the native M-CSF. The results show that the interchain disulfide bond of M-CSF is not essential for the natural folding of active M-CSF.

Identification of amino acid residues of Bacillus thuringiensis delta-endotoxin CryIAa associated with membrane binding and toxicity to Bombyx mori

Alanine substitution (A3) or deletion (D3) of residues 365 to 371 of Bacillus thuringiensis CryIAa insect toxin removed nearly all toxicity for Bombyx mori (> 1,000-fold less active than the wild type). The loss of larvicidal activity in the mutants was not caused by increased sensitivity to larval gut enzymes but could be attributed to significantly reduced binding to B. mori brush border membrane vesicles. Some or all of the affected amino acid residues may interact directly or indirectly with the B. mori membrane receptor(s). Such receptor binding appears to be directly correlated with insect toxicity.

Production of antibodies against Bacillus thuringiensis delta-endotoxin by injecting its plasmids

Bacillus thuringiensis insecticidal crystalline delta-endotoxin proteins are plasmid encoded. Specific antibodies against the delta-endotoxin were obtained in mice and rabbits by injecting isolated B. thuringiensis DNA plasmids into their muscles. Antibodies could be detected by ELISA as early as two weeks after the first injection. They formed immunoprecipitin lines with the toxin in the Ouchterlony agarose plate and neutralized the toxicity of the toxin. Because no special equipment, delivery mechanism or purification of the protein is required, this technique may provide a way to raise polyclonal antibodies to proteins encoded by bacterial plasmids and recombinant products.

Production by a baculovirus expression system of the APO-protein of L-gulono-gamma-lactone oxidase, a flavoenzyme possessing a covalently-bound FAD

L-Gulono-gamma-lactone oxidase, an enzyme functioning in L-ascorbic acid biosynthesis in higher animals, possesses a covalently-bound FAD as the prosthetic group. Catalytically-active enzyme was expressed in silkworm cells by a recombinant baculovirus encoding rat L-gulono-gamma-lactone oxidase. When recombinant enzyme was expressed under riboflavin-deficient conditions, most of it was found to be the apoprotein, as evidenced by an increase in enzymic activity upon addition of FAD to the assay mixture. Interestingly, the observed enzymic activity is thought to have been provoked by a noncovalent interaction between FAD and the apoprotein, since the covalent attachment of FAD was not demonstrated by a fluorometric gel-scanning experiment.

GATA-type zinc finger motif-containing sequences and chorion gene transcription factors of the silkworm Bombyx mori

To characterize a DNA-binding protein, BCFI, which regulates the expression of silkmoth chorion genes through binding to gene promoter elements identical to those recognized by the GATA family of transcription factors, we have carried out polymerase chain reaction amplifications of Bombyx mori genomic DNA using degenerate primers derived from the conserved DNA binding domain of mammalian GATA factors. Two single copy genes, BmGATA alpha and BmGATA beta, were identified, which encode sequences containing GATA-type zinc finger motifs. The BmGATA beta gene is expressed in follicular and Bm5 tissue culture cells, the two cell types that contain BCFI. No BmGATA alpha gene transcripts were detectable in the tissues that were tested. Upon overexpression in Escherichia coli, a peptide encompassing the BmGATA beta zinc finger motif was able to bind specifically to the BCFI recognition motif of the chorion gene promoters. A polyclonal antibody directed against the zinc finger domain of BmGATA beta was also used in gel retardation assays to confirm that factor BCFI is indeed encoded by the BmGATA beta gene. Conceptual translation of a complete cDNA clone encoding the BmGATA beta protein revealed that this protein has a size similar to that of an immunoreactive protein, presumably BCFI, which is present in follicular cell extracts.

[Silk waste--a further allergen in the bedroom]

From 1978 until 1993 we diagnosed 167 cases of inhalative allergy to silk-filled bed quilts. The patients experienced asthma attacks predominantly during the night. Occupational exposure to silk materials was found in six cases. The mean age at first manifestation of symptoms (31 years, range 8 to 58) was relatively high, indicating an aggressive inhalation allergen. Beside a case of occupational asthma in a silk filature, we present two patients with nightly respiratory symptoms: an 8-year-old boy, whose asthma immediately disappeared during his holidays away from home, and a 48-year-old woman diagnosed only eight years after the beginning of an asthma unresponsive to therapy. Elimination of the silk-waste-containing bed quilts led to complete recovery of respiratory symptoms. Prick and intracutaneous skin testing as well as scratch tests using material of silk-filled quilts and the RAST (Pharmacia k 73) to silk waste turned out to be sensitive diagnostic parameters. Many of these bed quilts filled with silk-waste are still used today. Beside the house-dust mites they are a further cause of nightly attacks and should also be considered in allergic work-up.

Atrial natriuretic peptide immunoreactivity in the eggs of the silkworm Bombyx mori

Synthesis and secretion of atrial natriuretic peptides (ANPs) are not confined to the atrium, but are also present in other tissues. Recently, we have found synthesis of ANP in the eggs of several vertebrate animals. The present study was undertaken to determine whether immunoreactive ANP (irANP) is present in the egg of an invertebrate, the silkworm (Bombyx mori L.). The serial dilution curve of egg extracts of silkworm was parallel to the standard curve of atriopeptin III. Analysis of ANP immunoreactivity by gel filtration chromatography and reverse-phase HPLC showed that the major immunoreactivity corresponded to rat proANP. The semipurified irANP of egg extracts produced a dose-dependent relaxation on rat aortic strips, which was blocked by preincubation with anti-ANP antiserum. Therefore, we suggest that ANP is synthesized in the silkworm egg.

DNA polymerase alpha-primase complex from the silk glands of the non-mulberry silkworm Philosamia ricini

The DNA content in the silk glands of the non-mulberry silkworm Philosamia ricini increases continuously during the fourth and fifth instars of larval development indicating high levels of DNA replication in this terminally differentiated tissue. Concomitantly, the DNA polymerase alpha activity also increases in the middle and the posterior silk glands during development, reaching maximal levels in the middle of the fifth larval instar. A comparable level of DNA polymerase delta/epsilon was also observed in this highly replicative tissue. The DNA polymerase alpha-primase complex from the silk glands of P. ricini has been purified to homogeneity by conventional column chromatography as well as by immunoaffinity techniques. The molecular mass of the native enzyme is 560 kDa and the enzyme comprises six non-identical subunits. The identity of the enzyme as DNA polymerase alpha has been established by its sensitivity to inhibitors such as aphidicolin, N-ethylmaleimide, butylphenyl-dGTP, butylanilino-dATP and antibodies to polymerase alpha. The enzyme possesses primase activity capable of initiating DNA synthesis on single-stranded DNA templates. The tight association of polymerase and primase activities at a constant ratio of 6:1 is observed through all the purification steps. The 180 kDa subunit harbours the polymerase activity, while the primase activity is associated with the 45 kDa subunit.

Synthesis of trehazolin beta-anomer

Synthesis of trehazolin beta-anomer (3) from a D-glucose derived azido alcohol (4), was accomplished. 2-Chloro-1-methylpyridinium iodide was used in place of 2-chloro-3-ethylbenzoxazolium tetrafluoroborate as a means of preventing concomitant anomerization. Evaluation of compound (3) reveals that the stereochemistry of the anomeric position is significant for generation of inhibitory activities towards trehalases.

Structures of the N-linked oligosaccharides of the membrane glycoproteins from three lepidopteran cell lines (Sf-21, IZD-Mb-0503, Bm-N)

The primary structures of the Asn-linked carbohydrate chains isolated from membrane glycoproteins of the three insect cell lines Mamestra brassicae (Mb-0503), Bombyx mori (Bm-N), and Spodoptera frugiperda (Sf-21) have been determined. Tryptic glycopeptides derived from the membrane fraction were digested with peptide-N-glycanase A. The resulting oligosaccharides were reductively aminated with 2-aminopyridine and identified by two-dimensional HPLC mapping in combination with exoglycosidase digestions. Oligomannose-type structures ranging from Man2GlcNAc2 to Man9GlcNAc2 occurred in all three cell lines. The pattern of Man5- to Man9GlcNAc2-isomers suggests an alpha-mannosidase trimming pathway very similar to that in mammalian cells. In each cell line, the small (Man2, Man3) oligosaccharides were partly fucosylated at the asparagine-linked GlcNAc residue, but distinct fucosylation patterns were observed: while only a low degree of alpha 1,3-fucosylation was detected in Sf-21 and Bm-N cells, the glycoproteins isolated from Mb-0503 cells contained 30% of alpha 1,3-fucosylated glycans, predominantly in the difucosylated form, i.e., with two fucoses linked to the same N-acetylglucosamine residue. Additionally, the following alpha 1,6-fucosylated (Bm-N cells) or difucosylated (Sf-21, Mb-0503 cells) GlcNAc-terminated structures were found: [formula: see text]