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

The use of caprylic acid for the extraction of the immunoglobulin fraction from egg yolk of chickens immunised with ovine alpha-lactalbumin

The extraction and purification of serum-derived immunoglobulin fraction in the egg yolk of hens by the combined treatment of the raw egg yolk with caprylic (octanoic) acid and ammonium sulphate is described. This simple two-step method proved to be both rapid, reproducible and suitable for batch processing of pooled egg yolk. The method recovered in excess of 130 mg of immunoglobulin per egg yolk. Two chickens were inoculated at two weekly intervals with 100 micrograms each of ovine alpha-lactalbumin over a ten week period. The alpha-lactalbumin antigen was purified by a hydrophobic-interaction chromatographic procedure and further purified by a gel excision-elution process. No precipitating antibodies could be demonstrated in gel diffusion techniques with this antibody. The specificity and specific activity of the antibody were monitored by western blotting and demonstrated the presence of highly specific antibodies to ovine alpha-lactalbumin in the treated egg yolk. The extraction procedure had no adverse effects on antibody titre. We concluded, and confirmed previous reports, that the use of chickens for the production of highly specific antibodies to mammalian proteins with particular reference to milk proteins presented numerous advantages over conventional procedures.

Domain structure of calpain: mapping the binding site for calpastatin

The peptide EKLGERDDTIPPEYRELLEKKTGV was synthesized to mimic the central consensus sequence of calpastatin, the specific, endogenous inhibitor of the calpains (EC 3.4.22.17). The peptide competitively inhibits hydrolysis of casein by either micro- or milli-calpain but does not affect the activity of other proteases. This inhibitory peptide was preferentially cross-linked to milli-calpain in the presence of calcium using the heterobifunctional cross-linking reagent m-maleimidobenzoyl-N-hydroxysuccinimide ester. Cross-linking of the peptide was blocked by calpastatin. The site of cross-linking for the peptide within milli-calpain was localized using random chemical cleavage of the enzyme-peptide complex at cysteine residues. Calpain fragments were identified as amino-terminal fragments through reactivity with a peptide-specific antiserum or as non-amino-terminal fragments through incorporation of 14C from 14CN. Analysis of the control and cross-linked fragments, from experiments using both milli-calpain and micro-calpain, maps the chemical cross-linking site to cysteine-497 and localizes the binding site for the calpastatin-like peptide to this highly conserved region of domain III of calpains catalytic subunit.

The human myocardial two-dimensional gel protein database: update 1994

An updated human heart protein two-dimensional electrophoresis (2-DE) database is presented. The database, which contains some 1388 protein spots characterised in terms of M(r) and pI, has been analysed further by Western immunoblotting and protein sequencing. From a total of 103 protein spots analysed, 49 have been identified by immunoblotting and 32 have been identified by protein sequencing. A further six proteins have tentatively been assigned by comparison with the human heart 2-DE protein database of Jungblut et al. (Electrophoresis) 1994, 15, 685-607). This database is being used in studies of alterations in protein expression in the diseased and transplanted human heart.

Purification and partial characterisation of barley glutamyl-tRNA(Glu) reductase, the enzyme that directs glutamate to chlorophyll biosynthesis

5-Aminolevulinic acid for chlorophyll synthesis in greening barley is formed from glutamate. One of the steps involved in the conversion of glutamate to 5-aminolevulinic acid involves a reduction of glutamyl-tRNA(Glu) to glutamate 1-semialdehyde and tRNA(Glu). An enzyme catalysing this reduction was purified from the stroma of greening barley chloroplasts. An approximately 270-kDa protein composed of 54-kDa identical subunits was identified as the barley glutamyl-tRNA(Glu) reductase after purification by Sephacryl S-300, Cibacron Blue-Sepharose, 2'-5'-ADP-Sepharose, Mono S, Mini Q and Superose 12 chromatography. The sequence of 18 amino acids from the N-terminus of the reductase is 50% identical to a cDNA-deduced domain of the Arabidopsis thaliana hemA protein and encoded in a barley hemA cDNA sequence. This is an unequivocal demonstration that the glutamyl-tRNA(Glu) reductase subunit of higher plants is encoded in a hemA gene of the nuclear genome. Heme at 4 microM concentration or glutamate 1-semialdehyde at 200 microM caused a 50% inhibition of the reductase activity. Micromolar concentrations of Zn2+, Cu2+ and Cd2+ also inhibited barley glutamyl-tRNA(Glu) reductase.

Proteasome-associated RNAs are non-specific

The RNA isolated from RNase-treated proteasome preparations from human erythrocytes, HeLa cells, the archaeon Thermoplasma acidophilum and also from recombinant proteasomes of T. acidophilum expressed in Escherichia coli was characterized. The RNA associated with structurally similar protein particles, namely with the two molecular chaperones, groEL from E. coli and with the thermosome from T. acidophilum, served as controls. Electrophoretic analysis on polyacrylamide gels of the radioactively end-labelled RNA revealed a very similar size distribution pattern, irrespectively of the protein particles from which they had been isolated. The predominant RNA species were in the size ranges 80 nucleotides and 120 nucleotides, respectively. Partial sequencing of their terminal regions by mobility-shift analysis revealed that, of the proteasomes from human erythrocytes, the approximately 80-nucleotide-long RNA consists of a heterogenous population of mostly tRNA species because they carried the tRNA-specific 3'-terminal sequence motif 5'-CCA-3'. The RNA in the size range 120 nucleotides isolated from the proteasomes of human erythrocytes and of T. acidophilum was also heterogeneous and displayed, in the terminal regions, a remarkable sequence similarity to the corresponding regions of the 5S rRNA from the same and different organisms. The total content of RNA of all the protein particles was quantified and found to be consistently sub-stoichiometric. All these findings strongly suggest that RNA associated with the proteasomes and with the molecular chaperones originate from the abundant cellular pool of the tRNAs and 5S rRNAs which bind non-specifically to these large protein particles.

Fibrin-targeted recombinant hirudin inhibits fibrin deposition on experimental clots more efficiently than recombinant hirudin

BACKGROUND

Although the indirect thrombin inhibitor heparin and the more potent direct inhibitor hirudin are useful in preventing thrombosis, a substantial opportunity remains for improving the thrombus selectivity of thrombin inhibitors.

METHODS AND RESULTS

To explore the effect of targeting an antithrombin to the surface of a clot, we covalently linked recombinant hirudin to the Fab' (or IgG) of a monoclonal antibody (59D8) that selectively binds to an epitope on fibrin that becomes exposed only after thrombin cleaves fibrinopeptide B. Antibody-coupled hirudin bound to an immobilized peptide of the fibrin beta-chain amino-terminal sequence and inhibited the peptidolytic activity of thrombin more efficiently than free hirudin. Thrombin inhibition dependent on binding to immobilized fibrin monomer was enhanced 1100-fold (P < .0001). Hirudin-59D8 Fab' was 10 times more effective than hirudin in inhibiting fibrin deposition on experimental clot surfaces in fibrinogen solution (P < .0001) and human plasma (P < .0001). The more effective inhibition of thrombin by the conjugate was supported by significantly diminished concentrations of fibrinopeptide A in the plasma supernatant of the clot (P = .0001). Inhibition of clotting by an uncoupled mixture of hirudin and 59D8 Fab' was indistinguishable from that by hirudin alone, indicating that the conjugate's greater inhibitory activity was due to the covalent linkage between antibody and hirudin.

CONCLUSIONS

Fibrin-targeted hirudin (in comparison with unmodified hirudin) significantly reduces fibrin deposition on the surface of experimental clots.

Purification and characterization of Helicobacter pylori alcohol dehydrogenase

Alcohol dehydrogenase of Helicobacter pylori (HPADH) was purified from the soluble fraction of cultured bacteria (strain NCTC 11637) by anion exchange and affinity chromatography. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the 160-fold purified enzyme displayed one protein band with a mobility that corresponded to an M(r) of 38,000. Although HPADH was capable of utilizing both NADP and NAD as cofactors in alcohol oxidation, it showed a strong preference for NADP over NAD. Kinetic studies revealed a Km value of 26 mM and a kcat value of 530 min-1 for ethanol/active site at 37 degrees C in 0.1 M potassium phosphate buffer (pH 7.4). The enzyme was considerably more active toward primary aliphatic alcohols than secondary alcohols. The Km and kcat values decreased as the chain length of the alcohol increased. Benzyl alcohol was a 100 times better substrate than ethanol in terms of kcat/Km values. At neutral pH, HPADH was more effective in aldehyde reduction than in alcohol oxidation. Because of its high specific activity for ethanol (14 units mg-1) under physiological conditions, HPADH can also effectively produce acetaldehyde at higher ethanol levels. This reversed function of HPADH and the production of toxic and reactive acetaldehyde could account for at least some of the gastrointestinal morbidity associated with H. pylori infection.

Characterization of a Trypanosoma cruzi poly(A)-binding protein and its genes

We have characterized the biochemical properties of a 66-kDa poly(A)-binding protein (PABP1) in the protozoan Trypanosoma cruzi and isolated two classes of cDNAs encoding the protein. In concordance, Southern blots showed the presence of 2 gene copies. The two cDNA classes differ in the length of adenosine-rich segments in the 5' untranslated region and in point changes scattered throughout the sequence, but their 1650-bp open reading frames encode identical proteins. A single mRNA of 5.5 kb was detected, indicating that the noncoding regions are unusually long. Both the mRNA and the protein are constitutively expressed in all stages of T. cruzi life cycle. The biochemical properties and sequence comparisons show that the T. cruzi PABP1 is similar to the PABP1 of other eukaryotic organisms. These results indicate that PABP1 has been conserved throughout eukaryotic evolution.

Human protein NEFA, a novel DNA binding/EF-hand/leucine zipper protein. Molecular cloning and sequence analysis of the cDNA, isolation and characterization of the protein

The cDNA libraries constructed from the human acute lymphoblastic leukemia cell line KM3 in the expression vector lambda gt11, were screened with the anti-CALLA (common acute lymphoblastic leukemia antigen) mAb (monoclonal antibody) J5. The selected J5-positive clone I containing a partial cDNA insert was isolated and sequenced. For completing the cDNA sequence the cDNA libraries were further screened by hybridization with the DIG (digoxigenin)-labelled DNA probe derived from clone I, the 5'-end region was analysed by 5'-RACE (rapid amplification of cDNA ends) using a sequence specific primer. In total a 1639 bp cDNA sequence was determined. The cDNA sequence contains a 1260 bp open reading frame and the untranslated 3'- and 5'-end sides. The 420 residue amino acid sequence, deduced from the cDNA sequence, unexpectedly differs fundamentally from CALLA (CD10) although clones I and II were J5-positive in immuno screening. The mature protein corresponding to the cDNA was isolated and characterized from the KM3 cells using polyclonal antisera raised against the in vitro expressed polypeptide from clone I. The protein is expressed on plasma membrane, in cytosol and is secreted into culture medium, its relative molecular mass was determined to be 55 kDa on SDS-PAGE. The deduced amino acid sequence from cDNA was confirmed by peptide sequences. The new protein contains a basic amino acid rich putative DNA binding domain (b) with a potential nuclear targeting signal, two helix-loop-helix (HLH) motif regions, concurrently EF-hand motifs, an acidic amino acid rich region (a) between the EF-hands, and a leucine zipper (Z) motif. This DNA binding protein therefore is characterized by a linked motif "b/HLH/a/HLH/Z". The protein was designated NEFA: DNA binding/EF-hand/acidic amino acid rich region.

Partial characterization of the protein and carbohydrate constituents of the egg shell of Hymenolepis diminuta (Cestoda)

The egg shell of Hymenolepis diminuta is composed of 31.7% protein and 2.9% carbohydrate (by weight), as determined using the Lowry and phenol-sulfuric acid assays and bovine serum albumin and glucose, respectively, as standards. Amino acid analyses of egg shells demonstrated the presence of 16 naturally occurring amino acids and six unidentified residues. Histidine accounted for > 22% of the amino acid residues. Hypochlorite-solubilized egg shells were fractionated using a combination of gel, hydroxyapatite and anion-exchange chromatography, and the fractions were analyzed by isoelectric focusing and gel chromatography. The results demonstrate that the shell consists of a complex mixture of proteins (almost all of which have acidic isoelectric points), glycoproteins and possibly free complex carbohydrates.

Preparative isolation of recombinant human insulin-like growth factor 1 by reversed-phase high-performance liquid chromatography

The isolation of recombinant human insulin-like growth factor 1 (rhIGF-1) is complicated by the presence of several rhIGF-1 variants which co-purify using conventional chromatographic media. These species consist primarily of a methionine-sulfoxide variant of the properly folded molecule and a misfolded form and its respective methionine-sulfoxide variant. An analytical reversed-phase high-performance liquid chromatography procedure using a 5-micron C18 column, an acetonitrile-trifluoroacetic acid (TFA) isocratic elution, and elevated temperature gives baseline resolution of the four species. Using this analytical method as a development tool, a process-scale chromatography step was established. The 5-micron analytical packing material was replaced with a larger-size particle to reduce back-pressure and cost. Since the TFA counter-ion binds tightly to proteins and is difficult to subsequently dissociate, a combination of acetic acid and NaCl was substituted. Isocratic separations are not good process options due to problems with reproducibility and control. A shallow gradient elution using premixed mobile phase buffers at the same linear velocity was found to give an equivalent separation at low load levels and minimized solvent degassing. However, at higher loading there was a loss of resolution. A matrix of various buffers was evaluated for their effects on separation. Elevated pH resulted in a significant shift in both the elution order and relative retention times of the principal rh-IGF-1 variants, resulting in a substantial increase in effective capacity. An increase in the ionic strength further improved resolution. Several different media were evaluated with regard to particle size, shape and pore diameter using the improved mobile phase. The new conditions were scaled up 1305-fold and resulted in superimposable chromatograms, 96% recovery and > 99% purity. Thus, by optimizing the pH, ionic strength and temperature, a high-capacity preparative separation of rhIGF-1 from its related fermentation variants was obtained.

Polyclonal antibody characterization of Babesia caballi antigens

In a previous study diagnostic B. caballi antigens with apparent molecular mass of 50 and 48 kDa were identified. Another antigen of 141 kDa was recognized by most but not all B. caballi sera tested. Here a further characterization of the three antigens is reported. Rabbits were vaccinated with gel-purified antigens and monospecific antibodies were obtained for the 141 and 48 kDa antigens. Antibodies raised against the 50 kDa antigen cross-reacted with the 48 kDa antigen, suggesting that these two antigens bear unique as well as common epitopes. After two-dimensional electrophoresis the 50 and 48 kDa antigens were present as horizontal bands over a pH range from approximately 5.0-7.0 with focused spots at a pH of 5.5 and 5.9, respectively. The 141 kDa antigen was not present after two-dimensional electrophoresis. None of the three antigens could be identified as a glycoprotein. Judging from the immunofluorescence antibody test staining pattern obtained with the rabbit sera the 141 kDa antigen is present on the surface of infected erythrocytes. The 50 and 48 kDa antigens are located in the parasite itself and probably not on the surface of infected erythrocytes. The punctate staining pattern observed with the 48 kDa antiserum suggests that this antigen might be located in or associated with the apical complex of the parasite.

Quantitation of electrophoretically separated proteins in the submicrogram range by dye elution

A new method for the fast, reliable and reproducible submicrogram quantitation of proteins separated by different electrophoretic techniques is presented. The method is based on a modified sensitive staining technique using Coomassie Brilliant Blue G-250 in colloidal solution combined with an optimized elution procedure of the bound dye in a 3% w/v solution of sodium dodecyl sulfate followed by photometric determination of dye concentration in the eluate. In addition a new method is provided for background correction, even suitable for gels showing strong background staining. The staining procedure allows the detection of 20 ng depending on the nature of the protein and the separation technique used. Quantitation is linear at least in the range from 50 ng to 10 micrograms and highly reproducible even under non-optimized conditions. The presented method can be applied to sodium dodecyl sulfate-electrophoresis, isoelectric focusing and two-dimensional electrophoresis.

Filipin staining of lipoproteins in polyacrylamide gels: sensitivity and photobleaching of the fluorophore and its use in a double staining method

We have developed a double staining procedure in which polyacrylamide gels are first stained with filipin to identify lipoproteins, and then with Coomassie Brilliant Blue (CBB) to identify proteins. Filipin staining when performed at 37 degrees C is both more rapid and more sensitive than previously published procedures. After only 5 min, 20 ng of low density lipoprotein (LDL) unesterified cholesterol/mm3 of band volume could be detected, and after 12 h, sensitivity reached 0.8 ng/mm3. A semilogarithmic relationship was found between the amount of LDL unesterified cholesterol applied and filipin fluorescence. Although rapid photobleaching of the fluorophore occurred during UV transillumination of these gels, such photobleaching actually resulted in maximizing of the signal:noise ratio, resulting in better definition of bands. Treatment of gels with filipin had no deleterious effects on the subsequent staining with CBB. This dual staining procedure should prove useful for studies in which both lipoproteins and proteins in plasma need to be documented in the same gel.

Effects of tyrosine-->phenylalanine mutations on auto- and trans-phosphorylation reactions catalyzed by the insulin receptor beta-subunit cytoplasmic domain

Activation of the insulin receptor kinase is closely associated with autophosphorylation of several tyrosine residues in the cytoplasmic domain of the receptor's two beta-subunits. To determine the contribution of these tyrosine phosphorylations to autoactivation of the receptor kinase, we have blocked phosphorylation at specific tyrosine by replacing these tyrosine residues, individually and in combination, with phenylalanine in a soluble 45-kD analog of the cytoplasmic insulin receptor kinase domain (CIRK). Kinetic studies of auto- and transphosphorylation with this panel of mutated CIRKs indicate that: (i) None of the tyrosines (953, 960, 1,146, 1,150, 1,151, 1,316, or 1,322) are necessary for catalysis: all single Y-->F mutants retain the ability to autoactivate comparable to the parent CIRK. (ii) Two of the tyrosine autophosphorylation sites, either tyrosine 1,150 or 1,151, contribute most (70-80%) of the autoactivation, because replacement of these two tyrosines by phenylalanine was the minimal change that abolishes autoactivation. (iii) A mutant CIRK having all seven reported tyrosine phosphorylation sites replaced by phenylalanine retained basal kinase activity but was incapable of autoactivation. These findings imply that autoactivation can occur without phosphorylation having occurred at any single site (953, 960, 1,146, 1,150, 1,151, 1,316, or 1,322), and autophosphorylation need not follow an ordered, sequential pathway beginning, for example, at tyrosine 1,146 as proposed for the intact insulin receptor.

Mouse trophoblast cell invasion of extracellular matrix purified from endometrial tissue: a model for peri-implantation development

We have investigated the invasive activity of mouse trophoblast cells during embryo implantation in vitro by culturing blastocysts with extracellular matrix (ECM) purified from mouse endometrium obtained on day 4 of pregnancy. Endometrium was dissected from lyophilized mouse uteri, and intact ECM was isolated by sequential precipitation in nonionic detergent and high salt. Electron microscopic examination of the ECM revealed typical collagen fibers plus an amorphous material resembling basement membrane. Electrophoretic analysis of the ECM revealed an enrichment of high molecular weight proteins, and immunoblotting indicated the presence of fibronectin, laminin, entactin, and type IV collagen, but not the intracellular proteins 2',3'-cyclic nucleotide-3'-phosphodiesterase or vimentin. Mouse blastocysts cultured with this ECM attached to it within 3 days, and the trophoblast cells began to migrate through the matrix in a manner resembling trophoblast invasion in utero. Unlike blastocysts cultured on plastic surfaces, the trophoblast did not flatten and become disorganized, but retained a polarized, spherical structure. Fluorescent microscopy with fluorescein isothiocyanate-labeled phalloidin revealed a high degree of microfilament organization and established that actin was absent from the ECM preparation. In the presence of a serum substitute, differentiation continued through yolk sac formation. Without serum components, yolk sac did not form; however, light and electron microscopic examination indicated that the invasive behavior of trophoblast cells persisted and was comparable to that of trophoblasts cultured in the presence of the serum substitute. A three-dimensional model for investigating trophoblast behavior in ECM from the endometrium should be of great value in elucidating the cellular and molecular events surrounding the process of blastocyst implantation.

Staphylococcal iron requirements, siderophore production, and iron-regulated protein expression

Despite the ability of staphylococci to grow in iron-restricted conditions in vivo, their iron requirements and the mechanisms possessed by them for the uptake of iron are poorly understood. Many bacteria are known to produce siderophores. By using the chrome azurol S universal method for the detection of siderophores, all 14 isolates of Staphylococcus aureus tested grew well under conditions of iron restriction and produced iron-regulated siderophore in large quantities, while all 19 isolates of coagulase-negative staphylococci (CoNS) grew poorly under conditions of iron restriction and produced low levels of iron chelator. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis profiles of S. aureus isolates revealed altered protein patterns due to iron restriction, while altered profiles were not seen in the CoNS group. The ability to grow in iron-restricted conditions, possibly with the assistance of siderophore-mediated iron uptake, may contribute to the increased pathogenicity of S. aureus when compared with that of the CoNS.

Antisuppression by a mutation in rpsM(S13) giving a shortened ribosomal protein S13

The phenotype associated with an rpsM(S13) mutation, originally isolated in Escherichia coli in a selection for pseudoreversion of streptomycin dependence, was studied in strains lacking the original mutations for antibiotic dependence. The rpsM mutation gives a decreased translational step time and a reduced growth rate. It functions as a strong antisuppressor to both the serU(Su1) amber suppressor and the trpT(Su9) opal suppressor, whereas the tyrT(Su3) amber suppressor is much less affected. The small ribosomal subunit from the rpsM mutant shows a reduced sedimentation coefficient but is able to form apparently normal 70S ribosomes as judged by ultracentrifugational analysis. Cloning and sequencing show that the rpsM mutation is a CAG to TAG alteration at codon position 100, giving an S13 protein which is shortened by 19 amino acids at its C-terminal end. This implies that the C-terminal domain of the protein that is involved in binding to 16S ribosomal RNA should be affected.

Induction of enoyl-CoA hydratase by LD50 exposure to perfluorocarboxylic acids detected by two-dimensional electrophoresis

The effect of in vivo exposure to perfluoro-n-octanoic and perfluoro-n-decanoic acids was examined in the rat liver by two-dimensional electrophoresis (2DE). Using nonequilibrium pH-gradient electrophoresis in the first dimension separation, proteins associated with the mitochondrial/peroxisomal cell fraction were observed and immunologically identified. Conspicuous inductions in peroxisomal enoyl-CoA hydratase and other proteins of the peroxisomal beta-oxidative pathway were observed following single-dose exposure to each compound. The abundance of the tentatively-identified mitochondrial equivalent, crotonase, was not altered by these intoxications. These results confirm previous observations of perfluorocarboxylic acid toxicity and support the use of 2D protein-pattern alterations in biomarker research. The ability to identify this type of alteration via 2DE, in association with specific toxic effects by chemically related compounds, may provide new and additional markers for chemical-induced tissue damage.

The molecular chaperone TF55. Assessment of symmetry

TF55-like factor from Sulfolobus solfataricus was purified to homogeneity and analyzed by electron microscopy and image analysis to determine the symmetries of these particles. Three different procedures were used to analyze the electron micrographs: (1) fuzzy-set based classification of the particles according to their rotational power spectra; (2) multivariate statistical analysis based on singular value decomposition; (3) circular harmonic analysis. Averages obtained from the three methods show unequivocally that the TF55-like complex presents a 9-fold symmetry.

Characterization of a 100-kDa heat-stable microtubule-associated protein from higher plants

In higher-plant cells, the different cell-cycle-dependent microtubule arrays are involved in a wide range of activities including chromosome segregation, cell-plate formation and cellulose microfibril distribution and orientation. A wealth of data, obtained using animal cells, has indicated that the differential stability and function of microtubules during cell-cycle and/or differentiation could be primarily regulated by selective microtubule-associated proteins (MAP). Compared to animal MAP, our knowledge of plant MAP is so far very limited. In this study, we have identified a maize heat-stable protein with apparent molecular mass 100 kDa (P-100) which binds to taxol-stabilized neurotubules and copolymerizes in vitro with purified neural tubulin. Moreover, P-100 cross-reacts with affinity-purified tau antibodies like a maize 83-kDa putative MAP described previously [Vantard, M., Schellenbaum, P., Fellous, A. & Lambert, A. M. (1991) Biochemistry 30, 9334-9340]. Polyclonal antibodies directed against P-100 were obtained and indicated that this protein is found in diverse higher-plant cultured cells suggesting the ubiquitous nature of this protein. P-100 can be phosphorylated in vitro by protein kinases present in a maize cytosol extract. Together, our data suggest that P-100 could be a higher plant MAP.

Characterization and localization of adenosine A2 receptors in bovine rod outer segments

Previous work from this laboratory has shown that retinal adenosine A2 binding sites are localized over outer and inner segments of photoreceptors in rabbit and mouse retinal sections. In the present study, adenosine receptor binding has been characterized and localized in membranes from bovine rod outer segments (ROS). Saturation studies with varying concentrations (10-150 nM) of 5'-(N-[2,8-3H]ethylcarboxamido)adenosine ([3H]NECA) and 100 micrograms of ROS membrane protein show a single site with a KD of 103 nM and a Bmax of 1.3 pM/mg of protein. Cold Scatchards, which used nonradiolabeled NECA (concentrations ranging from 10 nM to 250 microM) in competition with a fixed amount of [3H]NECA (30 nM), demonstrated the presence of a low-affinity site (KD, 50 microM) in addition to the high-affinity site. To confirm the presence of A2a binding sites, saturation analyses with 2-p-(2-[3H]-carboxyethyl)phenylamino-5'-N-ethylcarboxamido adenosine (0-80 nM) also revealed a single population of high-affinity A2a receptors (KD, 9.4 nM). The binding sites labeled by [3H]NECA appear to be A2 receptor sites because binding was displaced by increasing concentrations of 5'-(N-methylcarboxamido)adenosine and 2-chloroadenosine. ROS were fractionated into plasma and disk membranes for localization studies. Receptor binding assays, used to determine specific binding, showed that the greatest concentration of A2 receptors was on the plasma membranes. Therefore, adenosine A2 receptors are in a position to respond to changes in the concentration of extracellular adenosine, which may exhibit a circadian rhythm.

Purification and characterization of microbially expressed neomycin phosphotransferase II (NPTII) protein and its equivalence to the plant expressed protein

The gene encoding neomycin phosphotransferase II (NPTII) has been used routinely as a selectable marker in the production of genetically engineered crops. To facilitate the safety assessment of this protein, the same coding sequence used for plant transformation was introduced into Escherichia coli to produce gram quantities of this protein. A unique, simple, rapid and efficient purification method was developed to purify thirty grams of NPTII protein. The microbially produced NPTII was shown to be chemically and functionally equivalent to the NPTII protein expressed in and purified from genetically engineered cotton seed, potato tubers and tomato fruit. Microbially produced and plant produced NPTII proteins have comparable molecular weights, immuno-reactivities, epitope structures, amino terminal amino acid sequences, biological activities and both lack glycosylation. Demonstrating the equivalence of NPTII protein from these sources establishes the validity of using the microbially produced NPTII to assess the safety of the NPTII protein produced in genetically engineered crops.

Subunit structure of ATP synthase from Chloroflexus aurantiacus

An ATP synthase has been isolated from green nonsulfur photosynthetic bacterium Chloroflexus aurantiacus, a representative of a lower branch of eubacteria. The enzyme, reconstituted with the bacterial lipids into proteoliposomes, is shown to catalyze [32P]Pi-ATP exchange (at a rate of 180 nmol [32P]ATP/min/mg). The ATP synthase is composed of nine polypeptide species (60, 50, 33, 19, 16.5, 15.5, 14.5, 13, and 8 kDa as determined by urea-SDS-PAGE). The catalytic part of the ATP synthase (which is detached by chloroform treatment) contains the first four polypeptides. In the intact ATP synthase the 14.5 and 13 kDa polypeptides are connected by disulfide bonds to form a heterodimer of 25 kDa.

Activation of porcine pepsinogen A. The stability of two non-covalent activation intermediates at pH 8.5

Reaction products formed during activation of porcine pepsinogen A at pH 2 were characterized by native agar-gel electrophoresis and by denaturing SDS/PAGE. The results revealed the presence of non-covalent intermediates between prosegment peptides and pepsin. The complexes Leu1p-Leu44p/pepsin and Leu1p-Leu16p/pepsin were isolated (the prosegment residues are characterized by the suffix p; numbering of residues starts again from the N-terminus of pepsin). Relative to mature pepsin, the inherent milk-clotting activities of the intermediates were 3% and 18%, respectively. The intermediates were incubated at pH 8.5 for 20 min at 28 degrees C and the residual proteolytic activities were tested at pH 2. The stabilities at pH 8.5 were between those of pepsinogen and pepsin, Leu1p-Leu44p/pepsin being most stable. The implications of these findings for the conformational changes that occur during the activation of pepsinogen are discussed.

Separation of acidic barley endosperm proteins by two-dimensional electrophoresis

Proteins in barley aleurone and starchy endosperm from developing seeds were separated by two-dimensional (2-D) electrophoresis according to O'Farrell's method. The effect of different extraction methods on the separation was compared. The two best extraction methods were compared by amino acid analysis of extracts and residues. Some tissue-specific proteins in both tissues are described. Different methods for transfer of separated proteins onto membranes were compared. Amino terminal and internal sequences were determined after transfer of separated proteins or their proteolytic products onto membranes. Amino acid sequence data allowed the identification of 12 different proteins, while 6 remain unidentified and 8 appeared to have a blocked amino terminal.

Optimizing a method of protein extraction for two-dimensional electrophoretic separation of proteins from planarians (Platyhelminthes, Turbellaria)

Different procedures for microscale extraction of proteins from small amounts of tissue of planarians (Platyhelminthes, Turbellaria) to be analyzed by two-dimensional gel electrophoresis (2-D PAGE) are compared. Three extraction methods were assessed: (i) extraction of soluble proteins with nondenaturing Tris buffers, (ii) extraction with Tris buffer containing the anionic detergent sodium dodecyl sulfate (SDS), and (iii) denaturing extraction under reducing conditions in the presence of urea and Nonidet P-40 (NP-40) with or without SDS. Buffers combining minute concentrations of SDS (0.01%), denaturing concentrations of urea (8M) and alkaline pH solubilized the greatest number of proteins without detectable proteolysis. Neither the presence of protease inhibitors nor higher concentrations of SDS improved protein extraction. We have applied this method to planarians to detect proteins specific to the pharynx. The resulting two-dimensional pattern shows a larger number of specific spots than in previous extraction methods.

Purification and characterisation of an extracellular peroxidase from white-rot fungus Pleurotus ostreatus

A peroxidase was purified 98.3-fold from the culture filtrate of Pleurotus ostreatus with an overall yield of 12.4%. The molecular mass determined by gel filtration was found to be approx. 140 kDa. SDS-PAGE revealed that the enzyme consists of two identical subunits with a molecular mass of approx. 72 kDa. The pI value of this enzyme is approx. 4.3. The enzyme contains 41% carbohydrate by weight, and aspartic acid and asparagine (16.8%), and glutamic acid and glutamine (12.0%). The enzyme has the highest affinity toward synaptic acid and affinity towards various phenolic compounds containing methoxyl and p-hydroxyl groups, directly attached to the benzene ring. However, the enzyme does not react with veratryl alcohol and shows no affinity for nonphenolic compounds. The optimal reaction pH and temperature are 4.0 and 40 degrees C, respectively. The catalytic mechanism of the enzymic reaction is of the Ping-Pong type. The activity of the enzyme is competitively inhibited by high concentrations of H2O2 and its Ki value is 1.70 mM against H2O2. This enzyme contains approx. 1 mol of heme per mol of one subunit of the enzyme. The pyridine hemochrome spectrum of the enzyme indicates that the heme of P. ostreatus peroxidase is iron protoporphyrin IX. The EPR spectrum of the native peroxidase shows the presence of a high-spin ferric complex with g values at 6.102, 5.643 and 1.991.

Photopolymerization of polyacrylamide gels with methylene blue

Photopolymerization of polyacrylamide gels in the presence of methylene blue (100 microM) and a redox couple (1 mM sodium toluenesulfinate, a reducer, and 50 microM diphenyliodonium chloride, an oxidizer) has been investigated. The gel point, i.e. the time needed for onset of gelation upon illumination, has been found to lengthen progressively at lower temperatures and at lower light intensities. If the three catalysts are progressively diluted, the gel point does not vary for a threefold dilution, but gelation is greatly hampered below a 1:5 dilution of the three effectors. Photobleaching has been assessed as a function of liquid layer thickness (from 0.5 to 2 mm), of a progressive dye dilution (down to a fourfold dilution) and as a function of temperature. A maximum of elastic modulus is located in correspondence to a minimum of permeability (both situated at 5% cross-linker). It is found that methylene blue-activated polymerization produces polyacrylamide gels with elastic properties which are higher than in persulfate-activated gels, so far the most popular matrices for electrokinetic separations. Due to the ease of preparation, the full control of all experimental parameters, and the lack of oxidizing power of this catalyst system (as opposed to the strong oxidation power of persulfate catalysis), methylene blue catalysis is advocated as a valid alternative to other redox systems.

HSP86 and HSP84 exhibit cellular specificity of expression and co-precipitate with an HSP70 family member in the murine testis

This study extends to the protein level our previous observations, which had established the stage and cellular specificity of expression of hsp86 and hsp84 in the murine testis in the absence of exogenous stress. Immunoblot analysis was used to demonstrate that HSP86 protein was present throughout testicular development and that its levels increased with the appearance of differentiating germ cells. HSP86 was most abundant in the germ cell population and was present at significantly lower levels in the somatic cells. By contrast, the HSP84 protein was detected in the somatic cells of the testis rather than in germ cells. The steady-state levels of HSP86 and HSP84 paralleled the pattern of the expression of their respective mRNAs, suggesting that regulation at the level of translation was not a major mechanism controlling hsp90 gene expression in testicular cells. Immunoprecipitation analysis revealed that a 70-kDa protein coprecipitated with the HSP86/HSP84 proteins in testicular homogenates. This protein was identified as an HSP70 family member by immunoblot analysis, suggesting that HSP70 and HSP90 family members interact in testicular cells.

Purification and characterization of the urease enzymes of Helicobacter species from humans and animals

The urease enzymes of Helicobacter pylori, H. mustelae, H. felis, and H. nemestrinae have been purified to homogeneity by affinity chromatography and characterized. The native urease enzymes of the four organisms were found to be almost identical, with a pI of 6.1 and molecular masses of 480 to 500 kDa, as determined by electrophoretic mobility in nondenaturing polyacrylamide gels. Transmission electron microscopy of the native urease showed it to be a molecule approximately 13 nm in diameter, with hexagonal symmetry. Denaturation studies indicated that each urease enzyme molecule was composed of two nonidentical subunits with molecular masses of approximately 64 and 30 kDa. The subunits were present in a 1:1 ratio, suggesting a hexameric stoichiometry for the native molecule. The predicted molecular mass of H. pylori urease, based on subunit molecular weight and stoichiometry, is 568 kDa. N-terminal amino acid sequencing of the enzyme subunits from the four species revealed high levels of homology. The large subunits (UreB) were found to be 92 to 100% homologous, and the small subunits (UreA) were 75 to 95% homologous over the first 12 to 20 residues. The high degree of homology suggests a common ancestral origin and an important role for the urease enzymes of these organisms.

Multiplicity of clathrin light-chain-like polypeptides from developing pea (Pisum sativum L.) cotyledons

A comparative study has been made of clathrin-coated vesicles from developing pea (Pisum sativum L.) cotyledons and bovine brains in order to characterize the clathrin light chains from a plant system. Four polypeptides of 31 kDa, 40 kDa, 46 kDa and 50 kDa are considered as candidates for clathrin light chains in the developing pea cotyledons. The 31 kDa, 40 kDa, 46 kDa and 50 kDa polypeptides, together with the 190 kDa heavy chain, are dissociated as triskelions when coated vesicles of developing pea cotyledons are treated with 2 M urea. Partially purified 46 kDa and 50 kDa polypeptides have been demonstrated to bind to purified clathrin heavy chains. The 40 kDa, 46 kDa and 50 kDa polypeptides are sensitive to elastase. They are readily solubilized by neutralization of 10% trichloroacetic acid precipitates of clathrin. The 50 kDa polypeptide of plant clathrin-coated vesicles is heat-stable as are the light chains from bovine brains, while the heat stability of the 31 kDa, 40 kDa and 46 kDa polypeptides of plants is dependent on pH and ionic strength. The 40 kDa, 46 kDa and 50 kDa polypeptides bind calmodulin. The calcium binding properties of these polypeptides are ambiguous. The 40 kDa and 46 kDa polypeptides can be phosphorylated more extensively than the 31 kDa in vitro in the presence of polylysine, as can the smaller light chain of brains. The 50 kDa polypeptide can also be phosphorylated, even without the addition of polylysine. Unlike brain light chains, phosphorylation of the 31 kDa, 40 kDa, 46 kDa and 50 kDa polypeptides from peas is greatly reduced by N-ethylmaleimide (NEM). Our findings contrast with earlier reports of clathrin light chains of 30 and 38 kDa from zucchini and 57 and 60 kDa from carrots, respectively.

Quantitation of proteins separated in N, N'-1,2-dihydroxyethylenebisacrylamide-crosslinked polyacrylamide gels

A simple and rapid method for the quantitation of proteins separated either by sodium dodecyl sulfate-electrophoresis or by isoelectric focusing in slab gels is presented. The method is based on the solubility of polyacrylamide gels crosslinked with N, N'-1, 2-dihydroxyethylenebisacrylamide (DHEBA) in periodic acid. After electrophoretic separation proteins are stained with Coomassie brilliant blue G-250. DHEBA gels show considerable swelling during the staining and destaining process but can be shrunk to their normal size in a 10% (w/v) solution of ammonium sulfate. Stained bands are cut from the gel and solubilized in periodic acid. During dissolution the dye decolorizes. Protein concentration in the solution is determined by a modified Coomassie dye-binding assay. Quantitation is linear in the range of 100 ng to 5 micrograms and not disturbed by dissolved gel. Separations in N, N'-1, 2-dihydroxyethylenebisacrylamide-crosslinked gels show qualities similar to those in normal crosslinked gels.

Demonstration of the humoral immune response of horses to Babesia caballi by western blotting

Babesia caballi-infected or normal equine erythrocytes were solubilized in sodium dodecyl sulfate (SDS) buffer and analyzed by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting. Antigens were allowed to react with sera from horses experimentally or field-infected with B. caballi and with sera from non-infected horses. Major babesial antigens recognized by immune sera had apparent mol. wts of 141, 112, 70, 50, 48, 34, and 30 kDa. The polypeptides at 50 and 48 kDa were recognized earliest and throughout infection, but also weakly by 3/100 equine sera tested negative and 1/33 sera tested false positive by the complement fixation test (CFT) and immunofluorescence antibody test (IFAT). Thus, further characterization and purification of B. caballi antigens are required to identify target antigens for an improved enzyme immuno assay. Until such an assay is available, Western blotting can provide a specific tool for the diagnosis of B. caballi infections, particularly in cases of contradicting CFT and IFAT results.

Biochemical and physiological studies on two T-kininogen species using monoclonal antibodies

Rat T-kininogens were characterized in plasma, urine and liver slice incubation medium in different physiological conditions using monoclonal antibodies that allow to distinguish between the two forms of T-kininogen. T-kininogen purified from the plasma of both normal and inflamed Wistar and Sprague-Dawley rats was found to contain the two forms of T-kininogen, TI and TII, separated by non-denaturing polyacrylamide gel electrophoresis. The two forms were also found in the plasma of several strains of normal and inflamed rats, except in the plasma of the Buffalo rat which contained only TII-kininogen. The two forms of T-kininogen were also found in the media in which liver slices from inflamed and non-inflamed wistar rats had been incubated. The urine T-kininogen of normal rats was chiefly TI-kininogen, but both forms were found in the urine of inflamed rats. T-kininogen in the plasma of normal and inflamed rats was further characterized by chromatography on Con A-Ultrogel. In normal plasma, we observed a ratio of non-retained to retained T-kininogen of 0.41. The retained T-kininogen was eluted as two peaks, one eluted with 45 mM and the other with 120 mM alpha-methyl-D-glucoside. The ratio of non-adsorbed to adsorbed T-kininogen in inflamed Wistar rat plasma was 1.40 and the retained material was almost exclusively in a single peak, which eluted with 50 mM alpha-methyl-D-glucoside. The non-adsorbed and adsorbed fractions contained both forms of T-kininogen, but the protein bands in the non-retained fraction had greater mobilities on non-denaturing PAGE. SDS-PAGE analysis of T-kininogen deglycosylated by N-glycosidase F showed a major band with a molecular mass of 50 kDa, whereas the molecular mass of the native form was 66 kDa. We concluded that both forms of T-kininogen exist in the non-inflamed and the inflamed rat plasma, except for the Buffalo rat, and that T-kininogen displays a different chromatographic pattern on Con A-Ultrogel after inflammation suggesting altered glycosylation.

Two-dimensional gel electrophoretic analysis of human lens proteins

Human lens proteins from clear lenses were separated and identified using two-dimensional polyacrylamide electrophoresis. Isoelectric focusing, both equilibrium and non-equilibrium, was performed in the first dimension and SDS electrophoresis in the second dimension. Proteins were identified by Western blotting and sequencing techniques and by comparison with patterns obtained with purified crystallin fractions. Analyses were performed on total urea soluble proteins of lenses varying in age from fetal to 73 yr. Several hundred protein spots representing crystallins, cytoskeletal proteins and enzymes were resolved in the fetal lens. In the older lenses there was a dramatic increase in the number of protein species in the molecular weight range of the crystallins and a reduced number of discrete protein species visible at molecular weights greater than 50,000. Conversely, a number of proteins below approximately 15 kDa were visible even in the fetal lens. The number and amount of polypeptides in this molecular weight range were increased in the older lenses. Many of these low molecular weight species could be assigned to either the alpha-, beta- or gamma-crystallin fractions. An age dependent increase in the number of acidic species of both crystallins and other proteins, such as, glyceraldehyde 3-phosphate dehydrogenase was observed as well as the loss or mobility change of gamma-crystallin. Two-dimensional gel electrophoresis provides a sensitive and practical technique for characterizing all of the proteins of the human lens.

An update on protein stains: amido black, coomassie blue G, and coomassie blue R

Samples of amido black, Coomassie blue G, and Coomassie blue R obtained over a number of years were tested for dye content, impurities, and effectiveness for staining proteins after polyacrylamide gel electrophoresis and for protein dye-binding assays. Some impurities produced reactions resembling metachromasia with specific proteins, although instances of true metachromatic staining are also reported. Several simple assays are given for determining dye content and relative levels of impurities. Recommendations are made for selecting batches of commercial dyes which are most likely to perform satisfactorily.