Improved staining of proteins in polyacrylamide gels including isoelectric focusing gels with clear background at nanogram sensitivity using Coomassie Brilliant Blue G-250 and R-250

Assessment of the allergenic potential of foods derived from genetically engineered crop plants

This article provides a science-based, decision tree approach to assess the allergenic concerns associated with the introduction of gene products into new plant varieties. The assessment focuses on the source from which the transferred gene was derived. Sources fall into three general categories: common allergenic food proteins; less common allergenic foods or other known allergen sources; and sources with no history of allergenicity. Information concerning the amino acid sequence identity to known allergenic proteins, in vitro and/or in vivo immunologic assays, and assessment of key physiochemical properties are included in reaching a recommendation on whether food derived from the genetically modified plant variety should be labeled as to the source of the transferred gene. In the end, a balanced judgement of all the available data generated during allergenicity assessment will assure the safety of foods derived from genetically engineered crops. Using the approaches described here, new plant varieties generated by genetic modification should be introduced into the marketplace with the same confidence that new plant varieties developed by traditional breeding have been introduced for decades.

Stability of food allergens to digestion in vitro

An integral part of the safety assessment of genetically modified plants is consideration of possible human health effects, especially food allergy. Prospective testing for allergenicity of proteins obtained from sources with no prior history of causing allergy has been difficult because of the absence of valid methods and models. Food allergens may share physicochemical properties that distinguish them from nonallergens, properties that may be used as a tool to predict the inherent allergenicity of proteins newly introduced into the food supply by genetic engineering. One candidate property is stability to digestion. We have systematically evaluated the stability of food allergens that are active via the gastrointestinal tract in a simple model of gastric digestion, emphasizing the major allergens of plant-derived foods such as legumes (peanuts and soybean). Important food allergens were stable to digestion in the gastric model (simulated gastric fluid). For example, soybean beta-conglycinin was stable for 60 min. In contrast, nonallergenic food proteins, such as spinach ribulose bis-phosphate carboxylase/oxygenase, were digested in simulated gastric fluid within 15 sec. The data are consistent with the hypothesis that food allergens must exhibit sufficient gastric stability to reach the intestinal mucosa where absorption and sensitization (development of atopy) can occur. Thus, the stability to digestion is a significant and valid parameter that distinguishes food allergens from nonallergens.

Determination of affinities of a panel of IgGs and Fabs for whole enveloped (influenza A) virions using surface plasmon resonance

The affinity of a panel of neutralizing monoclonal IgGs and their Fab fragments has been measured for the first time with an enveloped type A influenza virus, by surface plasmon resonance (SPR) and the BIAlite instrument. Equilibrium constants could be calculated for four of the five mAbs tested. These were in the nanomolar range. The ranking order was very similar to that obtained with an affinity ELISA, (an equilibrium system) but as others have found, affinities were 2-10-fold lower as measured by SPR (a flow system). No data were obtained with mAb HC58 although it had one of the highest affinities using an ELISA format, and was 28-fold higher than another mAb (HC10) which gave good data by SPR. This may relate to the orientation of its binding on the virion surface. The Kdissoc. of the Fabs was only 3-10-fold higher compared to their IgGs. Fab from the lowest affinity IgG (HC10) could not be measured, possibly because it fell below the threshold for detection.

Solubilization of membrane-bound rod phosphodiesterase by the rod phosphodiesterase recombinant delta subunit

Retinal rod and cone phosphodiesterases are oligomeric enzymes that consist of a dimeric catalytic core (alpha'2 in cones and alphabeta in rods) with inhibitory subunits (gamma) that regulate their activity. In addition, a 17-kDa protein referred to as the delta subunit co-purifies with the rod soluble phosphodiesterase and the cone phosphodiesterase. We report here partial protein sequencing of the rod delta subunit and isolation of a cDNA clone encoding it. The predicted amino acid sequence is unrelated to any other known protein. Of eight bovine tissue mRNA preparations examined by Northern analysis, the strongest delta subunit-specific signal was present in the retina. A less intense signal was seen in the brain and adrenal mRNA. In bovine retinal sections, rod delta subunit anti-peptide antibodies label rod but not cone outer segments. delta subunit, added back to washed outer segment membranes, solubilizes a large fraction of the membrane-bound phosphodiesterase, indicating that this subunit binds to the classical membrane associated phosphodiesterase. The subunit forms a tight complex with native, but not trypsin-released phosphodiesterase, suggesting that the isoprenylated carboxyl termini of the catalytic subunits may be involved in binding of the delta subunit to the phosphodiesterase holoenzyme.

Methods for purification of glutathione peroxidase and related enzymes

The different preparative techniques and related analytical methods used for purification of glutathione peroxidase, glutathione transferase and glutathione reductase, described in papers published in the last ten years, have been reviewed in this article. Among the different purification techniques, chromatography has played a relevant role, being reported in all the papers reviewed, whereas other preparative techniques such as electrophoresis and isoelectric focusing were less employed and have been reported in only ca. 3% of cases. Frequently, several different chromatographic modes and several rechromatography steps have been employed. The use of at least three different chromatographic modes has been reported in 53% of total reviewed papers, whereas 41% of them employed two differents modes and in only 6% a single preparative chromatographic step was used. To evaluate losses and improve recovery, analytical methods for quantitation of protein and assay of enzymatic activity must be used in each purification step. Among these analytical techniques, gel electrophoresis, under denaturing conditions, has been widely used to assess purity of enzyme preparation. A discussion of the different activity assay methods used for these three enzymes is also presented in this article.

Methods for chromatographic and electrophoretic separation and assay of NADP oxidoreductases

The different techniques described in purification protocols for pyridine nucleotide-dependent enzymes have been reviewed, covering mainly the papers published in the past six years. Chromatography was reported in 100% of reviewed papers and among the chromatographic techniques, affinity chromatography was the most used (ca. 92%), followed by ion-exchange chromatography (ca. 79%), size-exclusion chromatography (ca. 64%) and hydrophobic chromatography (ca. 24%). Other chromatographic techniques were used infrequently. Each chromatographic technique has a different specific capacity and chemical selectivity and, therefore, the order of selection should be based on a precise knowledge of the nature of the sample and the amount of the target enzyme that it contains. Analytical electrophoresis was used in about 95% of the reviewed papers, with denaturing polyacrylamide gel electrophoresis (PAGE) being the most widely used mode (ca. 92%), followed by native PAGE (ca. 48%). The use of isoelectric focusing was reported in 14% of the papers, while preparative gel electrophoresis was used in only 8% of the cases. The use of other electrophoretic techniques was reported in only a few papers. The use of continuous enzymatic activity assay methods (spectrophotometric) was found in most papers, while high-performance liquid chromatography-based methods (discontinuous assays) were reported in only 11% of the reviewed articles.

Integration and expression of the high-molecular-weight glutenin subunit 1Ax1 gene into wheat

The unique bread-making characteristic of wheat flour is closely related to the elasticity and extensibility of the gluten proteins stored in the starchy endosperm, particularly the high-molecular-weight glutenin subunits (HMW-GS), which are important in determining gluten and dough elasticity. The quality of wheat cultivars depends on the number and composition of the HMW-GS present. We have introduced the HMW-GS 1Ax1 gene, known to be associated with good bread-making quality, into the Bob White cultivar of wheat (Triticum aestivum L.), in which it is not present in nature, by the biolistic bombardment of cultured immature embryos. Of the 21 independent transformed lines selected, 20 expressed the selectable bar gene, and nine the 1Ax1 gene. The amount of HMW-GS 1Ax1 protein produced in the different transgenic lines varied from 0.6% to 2.3% of the total protein, resulting in an increase of up to 71% in total HMW-GS proteins. The transgenic plants were normal, fertile, and showed Mendelian segregation of the transgenes. The accumulation of HMW-GS 1Ax1 was consistent and stable up to the R3 seed generation. These results demonstrate that it is possible to manipulate both the quantity and quality of HMW-GS, which influence the bread-making quality of wheat.

Expression of catalytically active barley glutamyl tRNAGlu reductase in Escherichia coli as a fusion protein with glutathione S-transferase

delta-Aminolevulinate in plants, algae, cyanobacteria, and several other bacteria such as Escherichia coli and Bacillus subtilis is synthesized from glutamate by means of a tRNA(Glu) mediated pathway. The enzyme glutamyl tRNA(Glu) reductase catalyzes the second step in this pathway, the reduction of tRNA bound glutamate to give glutamate 1-semialdehyde. The hemA gene from barley encoding the glutamyl tRNA(Glu) reductase was expressed in E. coli cells joined at its amino terminal end to Schistosoma japonicum glutathione S-transferase (GST). GST-glutamyl tRNA(Glu) reductase fusion protein and the reductase released from it by thrombin digestion catalyzed the reduction of glutamyl tRNA(Glu) to glutamate 1-semialdehyde. The specific activity of the fusion protein was 120 pmol.micrograms-1.min-1. The fusion protein used tRNA(Glu) from barley chloroplasts preferentially to E. coli tRNA(Glu) and its activity was inhibited by hemin. It migrated as an 82-kDa polypeptide with SDS/PAGE and eluted with an apparent molecular mass of 450 kDa from Superose 12. After removal of the GST by thrombin, the protein migrated as an approximately equal to 60-kDa polypeptide with SDS/PAGE, whereas gel filtration on Superose 12 yielded an apparent molecule mass of 250 kDa. Isolated fusion protein contained heme, which could be reduced by NADPH and oxidized by air.

High-affinity maltose/trehalose transport system in the hyperthermophilic archaeon Thermococcus litoralis

The hyperthermophilic marine archaeon Thermococcus litoralis exhibits high-affinity transport activity for maltose and trehalose at 85 degrees C. The K(m) for maltose transport was 22 nM, and that for trehalose was 17 nM. In cells that had been grown on peptone plus yeast extract, the Vmax for maltose uptake ranged from 3.2 to 7.5 nmol/min/mg of protein in different cell cultures. Cells grown in peptone without yeast extract did not show significant maltose or trehalose uptake. We found that the compound in yeast extract responsible for the induction of the maltose and trehalose transport system was trehalose. [14C]maltose uptake at 100 nM was not significantly inhibited by glucose, sucrose, or maltotriose at a 100 microM concentration but was completely inhibited by trehalose and maltose. The inhibitor constant, Ki, of trehalose for inhibiting maltose uptake was 21 nM. In contrast, the ability of maltose to inhibit the uptake of trehalose was not equally strong. With 20 nM [14C]trehalose as the substrate, a 10-fold excess of maltose was necessary to inhibit uptake to 50%. However, full inhibition was observed at 2 microM maltose. The detergent-solubilized membranes of trehalose-induced cells contained a high-affinity binding protein for maltose and trehalose, with an M(r) of 48,000, that exhibited the same substrate specificity as the transport system found in whole cells. We conclude that maltose and trehalose are transported by the same high-affinity membrane-associated system. This represents the first report on sugar transport in any hyperthermophilic archaeon.

Expression of a novel high-molecular-weight glutenin subunit gene in transgenic wheat

High-molecular-weight glutenin subunits (HMW-GS), one class of seed storage proteins, are important determinants of the bread-making quality of wheat flour. To change the amount and composition of these proteins via genetic engineering, a gene encoding a novel hybrid subunit under the control of native HMW-GS regulatory sequences was inserted into wheat. Of 26 independent transgenic lines identified by bialaphos selection, 18 expressed the cotransformed hybrid HMW-GS gene in their seed. The hybrid subunit accumulated to levels comparable to those of the native HMW-GS. These results show that a native HMW-GS gene promoter can be used to obtain high levels of expression of seed storage and, potentially, other proteins in transgenic wheat endosperm. Transgene expression was stable for at least three seed generations in the majority of lines. These experiments demonstrate the feasibility of constructing wheat plants with novel seed protein compositions.

A hyperthermostable protease of the subtilisin family bound to the surface layer of the archaeon Staphylothermus marinus

BACKGROUND

Staphylothermus marinus, an archaeon isolated from a geothermally heated marine environment, is a peptide-fermenting, sulphur-dependent organism with an optimum growth temperature of 92 degrees C. It forms grapes of cells, which adhere to each other and to sulphur granules via their surface layer. This glycoprotein layer forms a canopy which is held at a distance of about 70 nm from the cell membrane by membrane-anchored stalks, thereby enclosing a 'quasi-periplasmic space'. Two copies of a globular protease, which probably serves an exodigestive function related to the organism's energy metabolism, are attached near the middle of each stalk.

RESULTS

We have purified and characterized this protease with regard to its enzymatic properties and thermostability, and have sequenced its gene using an approach based entirely on the polymerase chain reaction. The precursor form is 1345 amino acids long; between residues 64-741, it contains a domain with clear homology to subtilisins, which is interrupted by two large insertions. The enzyme has a broad substrate specificity and a pH optimum of 9.0. It is fully stable from pH 3.2 to 12.7 and is resistant to heat-inactivation to 95 degrees C in the free form and to 125 degrees C in the stalk-bound form.

CONCLUSIONS

This protease is one of the most stable proteases known. Its high resistance towards denaturing agents makes it an interesting target for practical applications. Despite its large size, it is clearly a member of the subtilisin family and represents the only known enzyme that is a stoichiometric S-layer component.

Purification and characterization of a protein that permits early detection of lung cancer. Identification of heterogeneous nuclear ribonucleoprotein-A2/B1 as the antigen for monoclonal antibody 703D4

We have reported that a mouse monoclonal antibody 703D4, detects lung cancer 2 years earlier than routine chest x-ray or cytomorphology. We purified the 703D4 antigen to elucidate its role in early lung cancer biology, using Western blot detection after SDS-polyacrylamide gel electrophoresis. Purification steps included anion exchange chromatography, preparative isoelectric focusing, polymer-based C18-like, and analytical C4 reverse phase high performance liquid chromatography. After 25-50,000-fold purification, the principal immunostaining protein was > 95% pure by Coomassie staining. The NH2 terminus was blocked, so CNBr digestion was used to generate internal peptides. Three sequences, including one across a site of alternate exon splicing, all identified a single protein, heterogeneous nuclear ribonucleoprotein-A2 (hnRNP-A2). A minor co-purifying immunoreactive protein resolved at the final C4 high performance liquid chromatography step is the splice variant hnRNP-B1. Northern analysis of RNA from primary normal bronchial epithelial cells demonstrated a low level of hnRNP-A2/B1 expression, consistent with immunohistochemical staining of clinical samples, and increased hnRNP-A2/B1 expression was found in lung cancer cells. hnRNP-A2/B1 expression is under proliferation-dependent control in normal bronchial epithelial cell primary cultures, but not in SV40-transformed bronchial epithelial cells or tumor cell lines. With our clinical data, this information suggests that hnRNP-A2/B1 is an early marker of lung epithelial transformation and carcinogenesis.

Enzyme-linked immunosorbent assay with partially purified cytosoluble 28-kilodalton protein for serological differentiation between Brucella melitensis-infected and B. melitensis Rev.1-vaccinated sheep

The problem of differentiating sheep infected with Brucella melitensis from those vaccinated or exposed to cross-reaching organisms has not been resolved by conventional serological tests or through the use of the smooth lipopolysaccharide in primary binding assays. We therefore analyzed sera from ewes experimentally infected with B. melitensis H38, from ewes naturally infected with B. melitensis, and from B. melitensis Rev.1-vaccinated ewes by enzyme-linked immunosorbent assay with three antigenic fractions: O polysaccharide, a cytosoluble protein extract (CPE) from the rough strain B. melitensis B115, and a partially purified cytosoluble protein of 28 kDa (CP28) from the CPE. Immunoglobulin G anti-O polysaccharide and anti-CPE responses were detected in all groups of animals tested (Rev.1 vaccinated and B. melitensis infected). However, false-positive reactions with CPE occurred with sera from Brucella-free ewes. The use of partially purified CP28 abolished these false-positive reactions. Furthermore, no immunoglobulin G antibodies against CP28 were detected in sera from vaccinated ewes, whereas 80% (8 of 10) of ewes experimentally infected with B. melitensis H38 and 89% (25 of 28) of naturally infected ewes showed various degrees of anti-CP28 reactivity (absorbance values of between 0.5 and 2.5). The results obtained with CP28 showed the potential usefulness of this antigen to permit the detection of B. melitensis-infected ewes and their differentiation from B. melitensis Rev.1-vaccinated ones.

An abundant hydrophobin (ABH1) forms hydrophobic rodlet layers in Agaricus bisporus fruiting bodies

The SDS-insoluble protein fraction of Agaricus bisporus fruiting bodies was solubilized with trifluoroacetic acid. On SDS-PAGE this fraction was found to contain one abundant protein with an apparent M(r) of 16 kDa. The N-terminal amino acid sequence of this protein was determined and RT-PCR used to isolate a cDNA clone which upon sequencing identified the protein as a typical class I hydrophobin (ABH1). The gene (ABH1) was isolated and sequenced, and a second hydrophobin gene (ABH2) was found about 2.5 kbp downstream of ABH1. Purified ABH1 self-assembled at hydrophobic-hydrophilic interfaces, producing the typical rodlet layer known from other hydrophobins. Similar rodlets were observed on the surface of the fruiting body, while immunological localization showed the hydrophobin to be particularly abundant at the outer surface of fruiting bodies, in the veil and in the core tissue of the stipe. Transcripts of ABH1 were found only in fruiting-body hyphae. The ABH1 hydrophobin is probably solely responsible for the hydrophobicity of the fruiting-body surface but may also line air channels within fruiting bodies.

Structural analysis and identification of gel-purified proteins, available in the femtomole range, using a novel computer program for peptide sequence assignment, by matrix-assisted laser desorption ionization-reflectron time-of-flight-mass spectrometry

A procedure is described for structural characterization and identification of proteins, purified by either one- or two-dimensional gel electrophoresis in the low picomole to femtomole range. The purified proteins are first detected in the primary gels by the sensitive reverse staining procedure described by Fernandez-Patron et al. (Anal. Biochem. 1995, 224, 203-211) and consecutively reeluted from combined get pieces and concentrated in the tip of a Pasteur pipette in a secondary gel matrix consisting of either sodium dodecyl sulfate-polyacrylamide or agarose. The concentrated proteins are in-matrix-digested and the resulting peptides are separated by reverse-phase high performance liquid chromatography (HPLC) combined with microsequencing or analyzed by matrix-assisted laser desorption ionization--time of flight--mass spectrometry. Protein identification is based on sequence homology or on the peptide mass pattern. The matching peptide sequences can additionally be verified by matching their measured post-source decay spectra with the calculated fragmentation patterns of the isobaric candidate peptides appearing on the search list. This is done by a computer program referred to as MassFrag, described in this paper. We demonstrate that it is possible to identify protein that are only available in the femtomole range and whose sequences are stored in nonredundant protein databases or nucleotide and expressed sequence tag databases.

Proteins of cytosol and amniotic fluid increase the voltage dependence of human type-1 porin

Heat-stable proteins from human and porcine cytosol and human amniotic fluid were found to increase the voltage dependence of human type-1 porin reconstituted in planar phospholipid bilayers. Purification processes revealed that these regulatory molecules were characterized by anionic charge and apparent molecular weights of between 23 and 64 kDa. The human cytosol proteins exerted inhibitory activity only when added to the compartment with applied negative potential. The observed increase in voltage dependence of porin was due to the presence of specific proteins in cytosol and amniotic fluid, since human cerebral spinal fluid in comparable amounts had no significant effect on the channel properties. Furthermore, other anionic proteins and polypeptides investigated demonstrated no inhibitory activity, indicating that anionic charge alone could not mimic the molecular properties of the regulatory proteins. With respect to the well-documented expression of porin in the plasma membrane of various cells and species, the presented data give first clues for a biochemical regulation of the channel in this compartment.

Purification and identification of FOAD-II, a cytosolic protein that regulates secretion in streptolysin-O permeabilized mast cells, as a rac/rhoGDI complex

Mast cells permeabilized by treatment with streptolysin-O in the presence of Ca2+ and GTP-gamma-S can secrete almost 100% of their contained N-acetyl-beta-D-glucosaminidase. If these stimuli are provided to the permeabilized cells after a delay, the response is diminished and the ability of the cells to undergo secretion runs down progressively over a period of about 30 min. This is thought to be due to the loss of key proteins involved in the exocytotic mechanism. Using this effect as the basis of a biological assay, we have isolated a protein from bovine brain cytosol that retards the loss of responsiveness to stimulation by Ca2+ and GTP-gamma-S. Purification of this protein and peptide sequencing have enabled us to identify it as the small GTP-binding protein rac complexed to the guanine nucleotide exchange inhibitor rhoGDI. Both proteins are required to retard the loss of the secretory response, while purified rhoGDI applied alone accelerates the rundown.

Identification of glycosylated forms of wheat storage proteins using two-dimensional electrophoresis and blotting

Two-dimensional electrophoresis with acid-polyacrylamide gel electrophoresis (PAGE), followed by sodium dodecyl sulfate (SDS)-PAGE and SDS-PAGE of unreduced polypeptides followed by SDS-PAGE under reducing conditions, were used to separate and identify the different subgroups of gliadins and glutenins and to distinguish between covalent and noncovalent polymers of glutenins. Gels were blotted under semidry conditions according to Laurière (Anal. Biochem. 1993, 212, 206-211) to allow large polymers of glutenins to be transferred efficiently. Glycosylated polypeptides were detected on blots using either the method of Haselbeck and Hösel (Glycoconjugate J. 1990, 7, 63-74), or using anti-(xylose-containing N-glycan) antibodies (Laurière et al., Plant Physiol 1989, 90, 1182-1188). High and low molecular weight glutenin subunits were shown to aggregate through both disulfide bridges and noncovalent protein-to-protein interactions. Aggregated gamma-gliadins were also demonstrated. Glycans were detected on both gliadin and glutenin polypeptides. Covalently aggregated low molecular weight glutenins were shown to contain N-glycans with xylose, which demonstrated their sorting in the Golgi apparatus.

Three separate proteins constitute the magnesium chelatase of Rhodobacter sphaeroides

The insertion of magnesium into protoporphyrin IX is the first step unique to chlorophyll production and is catalyzed by magnesium chelatase. The Rhodobacter sphaeroides genes, bchI and bchD together, and bchH alone, were cloned and expressed with the pET3a vector in Escherichia coli strain BL21 (DE3). The 40-kDa BchI protein was synthesized in greater abundance compared to the 70-kDa BchD protein when both were expressed together from the same plasmid. The production of large amounts of the 140-kDa BchH protein in E. coli was accompanied by an accumulation of protoporphyrin IX. The accumulated protoporphyrin IX was bound specifically to BchH in an approximate molar ratio of 1:1. All three recombinant proteins were soluble; BchH was monomeric, Bchl was dimeric, while BchD appeared to be polymeric with a molecular mass of approximately 550 kDa. The BchH and BchI proteins were purified to apparent homogeneity while BchD was separated from BchI and partially purified. Magnesium was inserted into protoporphyrin IX and deuteroporphyrin by combining these three proteins in the presence of ATP. One monomer of BchH to one dimer of BchI gave the optimal magnesium chelatase activity and the activity was dependent on the amount of partially purified BchD added to the assay at the optimum BchH:BchI ratio. The reaction was dissected into two parts with an activation step requiring BchI, BchD, and Mg2+-ATP, and a metal-insertion step which in addition requires Mg2+, protoporphyrin IX, and BchH. The stoichiometric binding of protoporphyrin IX to BchH in vitro is direct evidence for BchH carrying out such a role in vivo whereas the other two proteins are involved in ATP activation and magnesium insertion.

Effect of structurally diverse peroxisome proliferators on rat hepatic sulfotransferase

Exposure to perfluorocarboxylic acids, pthalate esters, and some hypolipidemic agents results in the proliferation of peroxisomes in the rodent liver. The structural diversity of these compounds suggests mechanistic diversity in their toxicity as well. To establish reliable biomarkers of peroxisome proliferation (PP) in compounds with distinct chemical toxicities, this study investigated the effect of in vivo exposure to perfluoro-n-octanoic acid, perfluoro-n-decanoic acid, di(2-ethylhexyl)phthalate (DEHP) and clofibrate on two-dimensional electrophoretic protein patterns of rat hepatic sulfotransferases, ST1A1, ST1C1 and ST2A1. After exposure to peroxisome proliferative doses, both ST1A1 and ST1C1 abundance in whole liver homogenates was significantly reduced, but only as a result of perfluorocarboxylic and exposure. The well-established PPs, DEHP and clofibrate had no effect on sulfotransferase expression whatsoever. The observed down-regulation of these STs is significant with respect to their normal detoxication activities and its potential correlation to carcinogenesis warrants further study. The present investigation supports previous studies that demonstrate the unique features of perfluorocarboxylic acid toxicity, relative to classic peroxisome proliferators and endorses the continued use of 2D protein-mapping of Sts and other proteins as biomarkers of chemical toxicity.

Preparative electrophoresis on linear polyacrylamide-agarose composite gels

A preparative method for isolating centigram quantities of high molecular weight polypeptide chains with high resolution and recovery uses linear polyacrylamide/agarose composite (LPAC) gels as electrophoretic media from which the polypeptides can be easily extracted. The composites are prepared in a manner yielding linear copolymers of acrylamide and 1-allyloxy-2,3-propanediol within 2% agarose gels. After electrophoresis in sodium dodecyl sulfate (SDS), protein bands were rapidly visualized for excision by briefly immersing the gel in cold 0.1 M KCl which precipitates the protein-associated SDS. The gel slices are then freeze-thawed to disrupt the agarose matrix and promote syneresis of fluid upon centrifugation. The polypeptides are then separated from the polyacrylamide in the supernatant solution by precipitating with either acidic isopropanol, trichloroacetic acid, ammonium sulfate or other general protein precipitants. As determined with polypeptide chains of fibrinogen and its cross-linked derivatives, recoveries were virtually complete (95.4% +/- 2.2%), and were independent of molecular weights over the range tested (10(4) --10(6)).

Distinction between genotypes of Lupinus species by sodium dodecyl sulphate-gel electrophoresis and by capillary electrophoresis

Effective distinction was achieved among a wide range of lupin grain samples by either sodium dodecyl sulphate (SDS)-gel electrophoresis or capillary electrophoresis, based on grain-protein composition. Capillary electrophoresis was faster (< 1 h) and provided slightly greater distinction between the samples. On the other hand, SDS-gel electrophoresis could provide a greater through-put of samples in a 24 h period. Either technique could be used successfully to distinguish between lupin species and cultivars for taxonomic analysis or seed identification.

Human albumin solders for clinical application during laser tissue welding

BACKGROUND AND OBJECTIVE

Fifty percent human albumin solder significantly improves weld strength when compared to lower concentrations [Wright et al., ASLMS meeting, April, 1995]. We developed a method for preparing 50% human albumin that may be considered compatible for clinical applications.

STUDY DESIGN/MATERIALS AND METHODS

Fifty percent human albumin solder was prepared from 25% commercially available human albumin using a lyophilization technique. Assessment of sterility, viscosity, pH, and peak absorption wavelength were performed.

RESULTS

This report describes the methodology used to prepare a 50% human albumin solder that is compatible with clinical use. Maintenance of the structural integrity of the albumin was confirmed by polyacrylamide gel electrophoresis.

CONCLUSION

This solder preparation can be used alone or with the addition of exogenous chromophores. The final product is sterile, incorporates viral free protocols, maintains high viscosity, and can be applied easily during open or laparoscopic procedures.

The primary structure of a basic leucine-rich repeat protein, PRELP, found in connective tissues

We have determined the primary structure of a connective tissue matrix protein from the nucleotide sequence of a clone isolated from a human articular chondrocyte cDNA library. The major part of the amino acid sequence has also been determined by direct protein sequencing. The translated primary sequence corresponds to 382 amino acid residues, including a 20-residue signal peptide. The molecular mass of the mature protein is 41,646 Da. The main part of the protein consists of 10 leucine-rich repeats ranging in length from 20 to 26 residues, with asparagine at position 10 (B-type). The N-terminal part is unusual in that it is basic and rich in arginine and proline. There are four potential N-linked glycosylation sites present. In three of these sites, post-translational modifications are likely to be present since Asn was not found by direct protein sequencing. The amino- and carboxyl-terminal parts contain four and two cysteine residues, respectively, probably forming disulfide bonds by analogy with the other members of this family. The protein shows highest identity (36%) to fibromodulin and 33% to bovine lumican, two other leucine-rich repeat connective tissue proteins. Northern blot analysis showed the presence of an approximately 3.8-kilobase mRNA in different types of bovine cartilage and cultured osteoblasts, whereas RNAs isolated from bovine kidney, skin, spleen, thymus, and trabecular bone and rat calvaria were negative. Human articular chondrocyte and rat chondrosarcoma cell RNAs contained an additional mRNA of approximately 1.6 and 1.8 kilobases, respectively.

Post-translational processing of the highly processed, secreted periplasmic carbonic anhydrase of Chlamydomonas is largely conserved in transgenic tobacco

The periplasmic carbonic anhydrase (CA) gene CAH1 of Chlamydomonas reinhardtii codes for a highly processed secreted glycoprotein. The primary translation product of the CAH1 gene is targeted to the ER, where it is proteolytically processed to yield two different subunits, glycosylated, assembled into an active heterotetramer, and secreted. After replacing the target leader sequence with that from tobacco anionic peroxidase, expression of this gene in transgenic tobacco plants was investigated. SDS-PAGE gels of the purified protein from tobacco, showed that it migrated as a series of discrete bands (two large and one small) with slightly faster mobility than the comparable bands in the purified algal protein. The expressed protein in the plant was active, and staining with thymol and sulfuric acid confirmed that it was also glycosylated. The periplasmic CA1 (peri-CA1) also was found to be enriched in the intercellular fluid of transgenic tobacco, indicating it was secreted. The specific activity of the enzyme and its sensitivity to sulfonamide inhibitors were similar to that of the native algal enzyme. These results suggest that the post translational processing of Chlamydomonas peri-CA1 is largely conserved in a higher plant.

Identification of major proteins associated with Dictyostelium discoideum endocytic vesicles

Magnetic isolation of endocytic vesicles from Dictyostelium discoideum was accomplished after feeding the amoebae with iron oxide particles. Proteins associated with the endocytic vesicles were resolved by SDS-PAGE and digested ‘in-gel’ with endoproteinase Lys-C or Asp-N to generate peptides for amino acid sequencing. This strategy allowed the identification of the major protein constituents of the vesicles: namely, the A, B, D, E and 110 kDa subunits of a vacuolar type H(+)-ATPase, actin, a Rab 7-like GTPase, a p34 protein corresponding to a new cysteine proteinase and the 25 kDa product of a recently sequenced D. discoideum open reading frame.

Adenosine dialdehyde blocks the disappearance of two nerve growth factor-induced insoluble proteins

Two nonionic-detergent-insoluble proteins are induced early in the nerve growth factor (NGF)-induced neuronal differentiation of PC12 cells. The pools of these two proteins then disappear from the insoluble fraction after a few days of continued exposure of the cells to NGF. The methylation-inhibiting drug adenosine dialdehyde blocks the disappearance of these insoluble proteins, implicating a methylation-dependent step in the pathway that regulates the fate of these proteins.

Evaluation by SDS-PAGE and immunoblotting of residual antigenicity in hydrolysed protein formulas

BACKGROUND

Extensively hydrolysed protein formulas are widely used as an alternative diet for children with cow's milk allergy. Partially hydrolysed protein formulas have been noted in some studies as useful in the prevention of allergy in infants at high risk of atopy. Although normally well tolerated, these 'hypoallergenic' products have been reported to cause serious immunological reactions in very sensitive subjects.

OBJECTIVE

Starting from these considerations, we studied some commercial hydrolysed formulas in search of biological data supporting the observed clinical reactions.

METHODS

We set up an electrophoretic method sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) which allowed us to study the molecular weight of peptides contained in hydrolysed products. Then, using the immunoblotting technique we evaluated the reactivity of circulating IgE (from serum of children allergic to cow's milk proteins) with the residual intact proteins and with the peptides present in these formulas.

RESULTS

Both group of milk proteins (caseins and whey proteins) were important allergens for children included in this study. The presence of high-molecular polypeptides was shown in partial hydrolysed formulas as such and in extensive hydrolysed products after protein enrichment by trichloroacetic acid (TCA) precipitation. Intact residual proteins were mainly responsible for the formation of IgE-antigen complexes observed in immunoblotting. More rarely, polypeptides of partial hydrolysed formulas were involved in immunological responses.

CONCLUSIONS

Both partial and extensive hydrolysed formulas could induce clinical reactions in very sensitive subjects. These responses are mainly associated with allergy to the small amounts of residual intact proteins.

Glia-to-axon communication: enrichment of glial proteins transferred to the squid giant axon

The transfer of newly synthesized proteins from the glial sheath into the axon is a well-documented process for the squid giant axon. In this study, we used a novel approach to separate the transferred glial proteins (TGPs) from the endogenous axoplasmic proteins of the squid giant axon. Axoplasm, containing radiolabelled TGPs, was extruded as a cylinder and immersed in an intracellular buffer. After 1-30 min, the TGPs were enriched in the intracellular buffer, because they were eluted from the axoplasm into the intracellular buffer much faster than the endogenous axoplasmic proteins. Most of the TGPs enriched in the intracellular buffer did not pellet when centrifuged at 24,000 g for 20 min and were susceptible to protease digestion without the addition of Triton X-100. Additionally, transmission electron microscopic autoradiography of intact axons, containing radiolabelled TGPs, suggested that most TGPs were not associated with vesicular organelles within the axon. We conclude that most of the TGPs are not contained within vesicles in the axoplasm of the squid giant axon, as would be expected if the mechanism of glia-to-axon transfer were conventional exocytosis-endocytosis or microphagocytosis.

Meat allergy: II--Effects of food processing and enzymatic digestion on the allergenicity of bovine and ovine meats

OBJECTIVES

This study was designed to evaluate whether peptic treatment of BSA and OSA affects their allergenicity and to evaluate the effect of technological treatments of meat for infant feeding on the allergenicity of these proteins.

SUBJECTS

Twelve children (8 males and 14 females) suffering from atopic dermatitis (AD), aged 12 months to 4.33 years (mean age 2.21 +/- 1.05 years).

STUDY DESIGN AND METHODS

Children suffering from atopic dermatitis (AD), (AD), clinically reactive and SPT-positive to beef, underwent skin prick testing (SPT) and radioallergosorbent test (RAST) with BSA and OSA, before and after peptic treatment. They were tested also with commercially available homogenized bovine meat (HBM) and with freeze-dried bovine (FDBM) and ovine (FDOM) meats. Peptic digestion of BSA and OSA was carried out in a Dubnoff's water bath containing 0.05 mg/ml of pepsin. SPT and RAST were performed for 1 mg/ml of BSA and OSA digested 5 minutes, 2 hours and 4 hours with pepsin; homogenized bovine meat, and FDBM and FDOM. SPT results were expressed as diameters (in mm) of the wheal obtained after SPT; a diameter > or = 3 mm was considered as positive. RAST was considered positive for IgE values 5 > UI/ml.

RESULTS

SPT to native BSA and OSA were positive in all patients. Only 2 of the 12 children were SPT-positive to HBM, FDBM, and FDOM. After digestion, SPTs and were positive as follows: for BSA, 4/12 after 5 minutes peptic treatment, 2/12 after 2 hours and 2/12 after 4 hours; for OSA, 3/12 after 5 minutes peptic treatment, none after 2 and 4 hours. None of RASTs was positive after peptic attack.

CONCLUSIONS

Both proteolytic digestion and technological treatment reduced the allergenic potential of meat products.

The interaction of beta 2-microglobulin (beta 2m) with mouse class I major histocompatibility antigens and its ability to support peptide binding. A comparison of human and mouse beta 2m

The function of major histocompatibility complex (MHC) class I molecules is to sample peptides derived from intracellular proteins and to present these peptides to CD8+ cytotoxic T lymphocytes. In this paper, biochemical assays addressing MHC class I binding of both peptide and beta 2-microglobulin (beta 2m) have been used to examine the assembly of the trimolecular MHC class I/beta 2m/peptide complex. Recombinant human beta 2m and mouse beta 2ma have been generated to compare the binding of the two beta 2m to mouse class I. It is frequently assumed that human beta 2m binds to mouse class I heavy chain with a much higher affinity than mouse beta 2m itself. We find that human beta 2m only binds to mouse class I heavy chain with slightly (about 3-fold) higher affinity than mouse beta 2m. In addition, we compared the effect of the two beta 2m upon peptide binding to mouse class I. The ability of human beta 2m to support peptide binding correlated well with its ability to saturate mouse class I heavy chains. Surprisingly, mouse beta 2m only facilitated peptide binding when mouse beta 2m was used in excess (about 20-fold) of what was needed to saturate the class I heavy chains. The inefficiency of mouse beta 2m to support peptide binding could not be attributed to a reduced affinity of mouse beta 2m/MHC class I complexes for peptides or to a reduction in the fraction of mouse beta 2m/MHC class I molecules participating in peptide binding. We have previously shown that only a minor fraction of class I molecules are involved in peptide binding, whereas most of class I molecules are involved in beta 2m binding. We propose that mouse beta 2m interacts with the minor peptide binding (i.e. the "empty") fraction with a lower affinity than human beta 2m does, whereas mouse and human beta 2m interact with the major peptide-occupied fraction with almost similar affinities. This would explain why mouse beta 2m is less efficient than human beta 2m in generating the peptide binding moiety, and identifies the empty MHC class I heavy chain as the molecule that binds human beta 2m preferentially.

Lumenal sites and C terminus accessibility of the skeletal muscle calcium release channel (ryanodine receptor)

The membrane topology of the skeletal muscle ryanodine receptor (RyR1) was investigated using site-directed antibodies directed against amino acid sequences 2804-2930, 4581-4640, 4860-4886, and 4941-5037. Ab(2804-2930) bound with identical affinity to either closed or permeabilized sarcoplasmic reticulum vesicles, confirming the cytoplasmic location of this segment. Ab(4581-4640) did not bind to closed vesicles but bound well to permeabilized vesicles, supporting a lumenal location for this segment. Ab(4860-4886) did not bind to closed vesicles but exhibited weak binding to the permeabilized vesicles, suggesting that a portion of the epitope may be exposed on the lumenal surface. The C-terminal antibody (Ab(4941-5037)) bound weakly to closed vesicles, and binding was not significantly enhanced by permeabilizing vesicles with low concentrations of non-denaturing detergent. However, the C-terminal antibodies bound efficiently to vesicles which were transiently incubated at alkaline pH or subjected to trypsinolysis, conditions where few of the vesicles were permeabilized. These results support a model for the membrane topology of the ryanodine receptor as proposed by Takeshima et al. (Takeshima, H., Nishimura, S., Matsumoto, T., Ishida, H., Kangawa, K., Minamino, N., Matsuo, H., Ueda, M., Hanaoka, M., Hirose, T., and Numa, S. (1989) Nature 339, 439-445). The results also suggest that the native conformation of the C terminus is inaccessible to antibodies.

Protein mutations revealed by two-dimensional electrophoresis

High-resolution two-dimensional electrophoresis (2DE) can resolve many hundreds of proteins present in complex mixtures depending on the method of detection. These proteins can be characterised qualitatively, with respect to their electrophoretic mobilities (i.e. charge and apparent molecular mass) and quantitatively, using densitometry, to determine their amounts. There has been a widespread application of 2DE in the analysis and characterisation of protein mutations for a range of organisms. This review presents examples of the use of 2DE to study naturally occurring protein mutations and polymorphisms as well as the characterisation of induced protein mutations in prokaryotes and eukaryotes. Examples are presented to illustrate the use of 2DE to detect mutations affecting the electrophoretic mobility and biosynthesis of individual proteins as well as mutations leading to global alterations in cellular protein synthesis. The advantages and disadvantages of 2DE in the detection of protein mutations are discussed.

Destaining of Coomassie Brilliant Blue R-250-stained polyacrylamide gels with sodium chloride solutions

A novel method for destaining of polyacrylamide gels, stained with Coomassie Brilliant Blue R-250, is described, based on the use of 0.5 M NaCl in water as the destainer, requiring only 2-3 h. Concentrated (> 2 M) or dilute (< 0.1 M) salt solutions were unsuitable. The method affords the advantage that expensive organic solvents, such as methanol, acetic acid or trichloroacetic acid, are not needed. Furthermore, salt destaining results in darker purple-blue protein bands as compared to the pale blue color with e.g. methanol/acetic acid destaining.

Two-dimensional electrophoretic mapping of hepatic and renal stress proteins

Cellular stress proteins and molecular chaperones are responsive to a variety of stressors and therefore comprise an ideal set of proteins with the potential to be used as biomarkers of chemical toxicity. We have investigated the expression of a group of well established heat shock and glucose-regulated proteins in the rat liver and kidney using large-scale two-dimensional protein electrophoresis and computerized image analysis. Our goal was to determine the level of their expression in unstressed target tissues and map their coordinate positions on conventional format two-dimensional electrophoresis (2-DE) gels. All the proteins studied, except for Hsp25 (heat-shock protein) whose expression fell below the level of analyzable detection, were constitutively expressed in liver and kidney. With the exception of Hsp70, all the stress proteins analyzed were constitutively more abundant in the liver than the kidney. Comparison of the sum total of all stress protein abundances revealed a nearly threefold higher level of expression in the liver than the kidney. Our results suggest that this group of proteins has significant responsibilities in normal, unstressed cells, due to their constitutive abundance. Correspondingly, the 2-DE stress protein pattern established in this study may be very useful in toxicologic screening as well as describing a broad range of molecular effects of xenobiotic exposure.

The thermosome of Thermoplasma acidophilum and its relationship to the eukaryotic chaperonin TRiC

A high molecular-mass protein complex from the archaebacterium Thermoplasma acidophilum, referred to here as the 'thermosome', is built from two subunits (M(r) 58 and 60). The thermosome has been purified to homogeneity. The molecular mass of the native complex was determined to be 1061 +/- 30 Da by scanning transmission electron microscopy. It shows a weak ATPase activity and is able to bind denatured polypeptides. Averages obtained from electron micrographs of negatively stained molecules in the end-on and side-on orientations, respectively, were compared with those of the t-complex polypeptide 1 ring complex (TRiC), isolated from bovine testes. Both molecules consist of two stacked pseudo eightfold symmetric rings which build up a cylindrical particle with a large cavity in the center. Sequence alignments of peptides generated from both subunits of the thermosome and different subunits of TRiC reveal a high partial similarity to each other and to the archaebacterial chaperonin thermophilic factor 55 from Sulfolobus shibatae as well as to eukaryotic TCP1 proteins. These striking structural similarities confirm the proposition that all these molecules belong to a single protein family which is structurally and functionally related to the GroEL class of molecular chaperones.

The pancornulins: a group of small proline rich-related cornified envelope precursors with bifunctional capabilities in isopeptide bond formation

In this report, the pancornulins are identified as members of the spr (small, proline-rich) multigene family by amino acid sequence and mass spectrometry analyses. One of the pancornulins (14.9 kDa) is identical to the protein predicted by spr-1 clone 128. The other pancornulins (16.9 kDa and 22 kDa) are novel members of the spr family. Immunoelectron microscopy of purified cornified envelopes with a pancornulin-specific antibody established these proteins more definitively as cornified envelope precursors. In addition, two-dimensional electrophoretic analyses of keratinocyte extracts labeled enzymatically with dansylcadaverine (to identify amine acceptors) or dansylPGGQQIV (to identify amine donors) showed that both glutamine and lysine residues within the pancornulins participate in the isopeptide linkage characteristic of cornified envelope formation. These results contrasted with those obtained using involucrin, a prominent cornified envelope protein shown capable of acting only as an amine acceptor in this system. Novel partial cDNAs obtained after reverse transcription and polymerase chain reaction amplification of total messenger RNA with pancornulin-specific primers suggest that the spr multigene family may be even larger than previously described. The bifunctional reactivity of the pancornulins in cross-linking and the large number of family members identified to date suggest that the pancornulins and other spr-1-related proteins may be more important in cornified envelope formation than previously considered, perhaps functioning as "bridge" molecules during the early phases of cornified envelope assembly.

The resolution and biochemical characterization of subcomplexes of the main light-harvesting chlorophyll a/b-protein complex of Photosystem II (LHC II)

LHC II isolated from carnation leaves has been solubilized and resolved by a newly developed, vertical-bed non-denaturing isoelectric focusing in polyacrylamide slab gels to yield three trimeric subcomplexes focusing at pH 4.52, 4.42 and 4.37 (designated a, b and c, respectively), comprising approximately 38%, 24% and 38% of the chlorophyll. The spectroscopic data demonstrated a close similarity among LHC II subcomplexes concerning their chlorophyll content and organization. The most alkaline and the most acidic subcomplex contained the 27 kDa polypeptide of LHC II while the intermediate pI fraction contained both LHC II polypeptides, i.e. 27 kDa and 26 kDa ones associated at 2:1 stoichiometry. The 27 kDa polypeptide could be resolved by denaturing isoelectrofocusing into 10 pI molecular isoforms covering 5.90-4.20 pH range. Three of the isoforms were found in the subcomplexes a and b and eight in the subcomplex c. The 26 kDa polypeptide comprised the unique pI molecular isoform focusing at pH 5.61.

Non-detergent sulphobetaines: a new class of mild solubilization agents for protein purification

The action of non-detergent sulphobetaines (NDSBs) as new mild agents for protein purification is described. The solubilization effects of non-detergent sulphobetaines are shown in different examples; all obtained under non-denaturing conditions: (1) microsomal proteins extraction; (2) recovery after dialysis of nuclear proteins; (3) reduction of precipitation in isoelectric focusing experiments under non-denaturing conditions; and (4) purification of a membrane-bound serine protease from Plasmodium falciparum involved in erythrocyte invasion by malaria merozoites. The absence of a significant denaturation effect induced by NDSBs is demonstrated by tests on beta-galactosidase and alkaline phosphatase. A simple NDSB synthesis and some possible explanations of the action of NDSBs are also presented.