Effect of zwitterionic surfactants on the separation of proteins by capillary electrophoresis

The effect of zwitterionic surfactants on capillary electrophoretic separation of proteins was investigated using an uncoated silica capillary column and different buffers containing zwitterionic surfactants. The effects of N-alkyl-N,N-dimethyl ammonio-1-propane-sulfonates on the electrophoretic mobility of three different proteins, namely albumin, lysozyme and myoglobin, were examined. The addition of N-alkyl-N,N-dimethylammonio-1-propane sulfonate in phosphate saline buffer is important in minimizing protein-capillary wall interactions, and facilitated an efficient electrophoretic mobility of myoglobin and lysozyme. The separation efficiency of proteins also depends on the injection pressure for the control of migration time and the peak sharpness. The electrophoretic conditions were applied to evaluate the separation of lysozyme, myoglobin and albumin. The zwitterion surfactants can form a dynamic coating on the capillary surface, thereby reducing the number of adsorption sites to which proteins may adsorb.

Complete removal and exchange of sodium dodecyl sulfate bound to soluble and membrane proteins and restoration of their activities, using ceramic hydroxyapatite chromatography

Up to now, removal of sodium dodecyl sulfate (SDS) from proteins in terms of restoration of their activity was an unsolved problem. A general procedure using ceramic hydroxyapatite (HAP) chromatography was developed for the complete removal of SDS bound to soluble or membrane proteins. This procedure involves (i) the binding of the SDS-protein complexes onto the ceramic hydroxyapatite column, (ii) extensive washing of bound proteins with phosphate buffer containing a mild detergent to exchange SDS, (iii) elution of the retained protein by increasing the phosphate concentration. Using this approach, complete exchange of [35S]SDS into a nonionic detergent such as dodecyl maltoside was achieved with a 90-100% protein recovery. The efficiency of protein-bound SDS removal is very likely due to the combined effect of phosphate ions and the hydrophobic tail of nonionic detergent: acting together, they are able to displace SDS molecules from their protein-binding sites. The advantages of this HAP-mediated SDS removal method include high efficiency, rapidity, simplicity and general applicability to a wide variety of detergents and soluble or membrane proteins. Of utmost importance, SDS-treated P-glycoprotein, glutamate dehydrogenase, and lysozyme fully recovered their enzymatic activities after HAP chromatography, including lysozyme electroeluted from SDS-polyacrylamide gel electrophoresis. This demonstrates that reactivation of SDS-treated protein can be achieved, provided that SDS is completely removed under mild conditions.

Molecular characterization of a germination-specific muramidase from Clostridium perfringens S40 spores and nucleotide sequence of the corresponding gene

The exudate of fully germinated spores of Clostridium perfringens S40 in 0.15 M KCI-50 mM potassium phosphate (pH 7.0) was found to contain another spore-lytic enzyme in addition to the germination-specific amidase previously characterized (S. Miyata, R. Moriyama, N. Miyahara, and S. Makino, Microbiology 141:2643-2650, 1995). The lytic enzyme was purified to homogeneity by anion-exchange chromatography and shown to be a muramidase which requires divalent cations (Ca2+, Mg2+, or Mn2+) for its activity. The enzyme was inactivated by sulfhydryl reagents, and sodium thioglycolate reversed the inactivation by Hg2+. The muramidase hydrolyzed isolated spore cortical fragments from a variety of wild-type organisms but had minimal activity on decoated spores and isolated cell walls. However, the enzyme was not capable of digesting isolated cortical fragments from spores of Bacillus subtilis ADD1, which lacks muramic acid delta-lactam in its cortical peptidoglycan. This indicates that the enzyme recognizes the delta-lactam residue peculiar to spore peptidoglycan, suggesting an involvement of the enzyme in spore germination. Immunochemical studies indicated that the muramidase in its mature form is localized on the exterior of the cortex layer in the dormant spore. A gene encoding the muramidase, sleM, was cloned into Escherichia coli, and the nucleotide sequence was determined. The gene encoded a protein of 321 amino acids with a deduced molecular weight of 36,358. The deduced amino acid sequence of the sleM gene indicated that the enzyme is produced in a mature form. It was suggested that the muramidase belongs to a separate group within the lysozyme family typified by the fungus Chalaropsis lysozyme. A possible mechanism for cortex degradation in C. perfringens S40 spores is discussed.

A novel procedure for the extraction of protein deposits from soft hydrophilic contact lenses for analysis

PURPOSE

A quick, simple, and efficient extraction technique was developed for the removal of protein from soft hydrophilic contact lenses.

METHODS

An extraction solvent consisting of a 50:50 mix of 0.2% trifluoroacetic acid and acetonitrile was used to remove protein from in vitro laboratory-deposited and human-worn contact lenses. The protein removed was analyzed using HPLC, bicinchoninic acid (BCA) analysis, and SDS-PAGE gel electreophoresis.

RESULTS

Extraction efficiency for lysozyme from laboratory-deposited Group IV lenses was determined to be approximately 100%. Group IV human-worn contact lenses were extracted and analyzed for lysozyme by HPLC and total protein by bicinchoninic acid (BCA) analysis. Groups I, II, III, and IV contact lenses deposited with an artificial tear protein solution and human-worn lenses were extracted and analyzed by SDS-PAGE gel electreophoresis and micro-BCA.

CONCLUSIONS

The ACN/TFA procedure offers a simple, quick, and efficient extraction technique for removal of protein from contact lenses for subsequent analysis.

Characterisation of non-porous magnetic chelator supports and their use to recover polyhistidine-tailed T4 lysozyme from a crude E. coli extract

The use of high capacity micron-sized non-porous magnetic metal chelator adsorbents for the direct recovery of a recombinant metal-binding protein from crude liquors is described. Selectivity and interaction strength of magnetic chelator particles were assessed using a set of native proteins with known behaviour towards commercially available immobilised metal chelate adsorbents. Particles charged with Cu2+ were highly effective in recovering a recombinant histidine-tailed T4 lysozyme fusion protein directly from crude E. coli extracts in a single step. Levels of recovery and purity were high and compared favourably with those achieved by chromatography of pre-clarified extracts on Cu(2+)-IDA Sepharose. The magnetic approach offers advantages such as the avoidance of clarification to prevent fouling of chromatography columns, steps that become especially significant at large scale. By detailed characterisation of the magnetic chelators the practical use of tailed T4 lysozyme for repeated production of periplasmic products is a realistic prospect.

Optimization of the capillary zone electrophoresis loading limit and resolution of proteins, using triethylamine, ammonium formate and acidic pH

Capillary zone electrophoresis (CZE) of five model proteins (lysozyme, myoglobin, ribonuclease A, alpha-lactalbumin, and trypsinogen), using ammonium formate as the electrophoretic buffer and triethylamine (TEA) as a buffer additive at pH 2.5, was used for protein separation. The electrophoretic behavior of these proteins was examined with respect to various concentrations (10-40 mM) of TEA and of ammonium formate. Based on the experimental parameters of electrophoretic resolution, current, and peak separation time, an electrolyte (30 mM each of TEA and ammonium formate) was empirically derived as the optimum for scale-up separation. The loading limit for proteins, covering a wide range of injection volumes (60-990 nl) and amount of protein (1-21 pmol of each protein), was investigated on 75 and 100 microns I.D. untreated fused-silica capillaries. Protein adsorption (average < 15%) was experimentally determined using this volatile buffer system.

Purification, characterization, and biosynthesis of bovine cartilage lysozyme isoforms

The cationic protein, lysozyme, has an extracellular distribution in cartilage; however, its biological role in this tissue still remains unclear. This study describes a simple and high yielding procedure for the purification of four novel isoforms of lysozyme from the functionally different articular (metacarpalphalangeal joint) and nonarticular (nasal septum) bovine cartilages. Chromatography of the cartilage extracts on S-Sepharose revealed the presence of four major lysozyme active peaks each of which was further purified to homogeneity by gel filtration and reversed-phase chromatography. Each peak yielded a different molecular mass when analyzed by ion spray mass spectrometry, and material isolated from either cartilage source displayed an identical molecular mass for each lysozyme preparation. N-terminal amino acid sequence and amino acid composition analyses confirmed the presence of four novel lysozyme isoforms in both bovine articular and nonarticular cartilages. The lytic activity of each lysozyme isoform toward Micrococcus lysodeikticus was dependent on both the ionic strength and pH of the buffer, where an increase in activity accompanied an increase in ionic strength. The lysozymes were shown to be synthesized by chondrocytes in vitro, which in addition to the relatively high chemical amounts of lysozyme present in cartilage, would suggest that this small cationic protein has some as yet undetermined biological role within the cartilage extracellular matrix.

Separation of proteins and peptides by capillary electrochromatography in diol- and octadecyl-modified etched capillaries

This study involves the evaluation of a capillary electrochromatography method based on etching the inner walls of a fused-silica tube, which is subsequently modified by a silanization/hydrosilation reaction scheme. Two different organic moieties, octadecyl and diol, are attached to the etched capillary wall. The performance of these two columns is compared to a bare capillary using peptide (angiotensins) and protein samples. It is concluded that the etching process increases the surface area of the inner wall sufficiently to induce solute-bonded phase interactions for the capillaries modified with the octadecyl and diol moieties. The separation capabilities of the two modified capillaries are not the same, presumably due to differences in the chemical properties of the two ligands. When compared to a bare capillary where separation is due only to electrophoretic mobility effects, the bonded etched capillaries also exhibit significant differences in separation factors for the same solutes under identical experimental conditions.

Purification and characterization of two bifunctional chitinases/lysozymes extracellularly produced by Pseudomonas aeruginosa K-187 in a shrimp and crab shell powder medium

Two extracellular chitinases (FI and FII) were purified from the culture supernatant of Pseudomonas aeruginosa K-187. The molecular weights of FI and FII were 30,000 and 32,000, respectively, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and 60,000 and 30,000, respectively, by gel filtration. The pIs for FI and FII were 5.2 and 4.8, respectively. The optimum pH, optimum temperature, pH stability, and thermal stability of FI were pH 8, 50 degrees C, pH 6 to 9, and 50 degrees C; those of FII were pH 7, 40 degrees C, pH 5 to 10, and 60 degrees C. The activities of both enzymes were activated by Cu2+; strongly inhibited by Mn2+, Mg2+, and Zn2+; and completely inhibited by glutathione, dithiothreitol, and 2-mercaptoethanol. Both chitinases showed lysozyme activity. The purified enzymes had antibacterial and cell lysis activities with many kinds of bacteria. This is the first report of a bifunctional chitinase/lysozyme from a prokaryote.

Conformation of T4 lysozyme in solution. Hinge-bending motion and the substrate-induced conformational transition studied by site-directed spin labeling

T4 lysozyme and mutants thereof crystallize in different conformations that are related to each other by a bend about a hinge in the molecule. This observation suggests that the wild type protein may undergo a hinge-bending motion in solution to allow substrate access to an otherwise closed active site cleft [Faber, H.R., & Matthews, B.W. (1990) Nature 348, 263-266]. To test this hypothesis, either single or pairs of nitroxide side chains were introduced into the protein to monitor tertiary contact interactions and inter-residue distances, respectively, in solution. A set of constraints for these structural parameters was derived from a reference state, a covalent enzyme-substrate adduct where the enzyme is locked in the closed state. In the absence of substrate, differences in both inter-residue distances and tertiary contact interactions relative to this reference state are consistent with a hinge-bending motion that opens the active site cleft. Quantitative analysis of spin-spin interactions between nitroxide pairs reveals an 8 A relative domain movement upon substrate binding. In addition, it is demonstrated that the I3P mutation, which produces a large hinge-bending angle in the crystal, has no effect on the solution conformation. Thus, the hinge motion is not the result of the mutation but is an integral part of T4 lysozyme catalysis in solution, as suggested recently [Zhang, X.J., Wozniak, J.A., & Matthews, B.W. (1995) J. Mol. Biol. 250, 527-552]. The strategy employed here, based on site-directed spin labeling, should be generally applicable to the study of protein conformation and conformational changes in solution.

Modification of polystyrenic matrices for the purification of proteins. Effect of the adsorption of poly(vinyl alcohol) on the characteristics of poly(styrene-divinylbenzene) beads for use in affinity chromatography

A poly(styrene-divinylbenzene) (PSDVB) chromatography matrix, CG1000-sd (TosoHaas), has been modified using poly(vinyl alcohol) (PVA) to create a matrix suitable for the attachment of functional groups for the selective purification of proteins. The characteristics of the modified matrix have been studied using a BET nitrogen adsorption/desorption technique and it has been found that the adsorption of PVA results in the bead micropores being filled whilst the bead macropores are left essentially unaltered. There was no protein adsorption onto the modified matrices. A dye ligand (Procion Blue MX-R) has been covalently attached to PVA-PSDVB matrix and the lysozyme capacities of the PVA-PSDVB matrix have been determined. The matrix compares well with commercial Blue Sepharose Fast Flow, an affinity matrix on cross-linked agarose. The dye-PVA-PSDVB matrix is stable when subjected to sanitisation with sodium hydroxide.

Direct purification of lysozyme using continuous counter-current expanded bed adsorption

We describe the application of a novel technique for the continuous counter-current chromatography of proteins. The unit operation has shown potential in extracting targeted species from unclarified feedstocks, delivering clarified streams of purified product. The adsorbent used in this equipment consists of a perfluorocarbon matrix, coated with poly(vinyl alcohol), and derivatized with the triazine dye Procion Red HE-7B. Purification of lysozyme from egg-whites and enriched bovine milk could be carried out continuously. The former was extracted in 90.5% yield at a rate of 7400 U/min, achieving a purification factor of 19.4. Lysozyme from the enriched milk sample was extracted continuously at a rate of 41000 U/min, in 66.0% yield. The continuous products streams in both cases were fully clarified, thus enabling their direct application to a final polishing step, if desired.

Protein purification and nucleotide sequence of a lysozyme from the bacteria-induced larvae of the fall webworm, Hyphantria cunea

A protein with lytic activity against Micrococcus luteus was purified from the hemolymph of the fall webworm, Hyphantria cunea, larvae challenged with live E. coli. A bacteriolytic protein of about 14,000 daltons in mass was purified by cation exchange chromatography and reverse-phased HPLC. The optimum pH and optimum temperature range for activity were around pH 6.2 and 50 degrees C, respectively, in a 100 mM phosphate buffer. The amino-terminal amino acid sequence of this protein was determined and the corresponding cDNA was isolated and analyzed. The deduced protein of 142 amino acid residues was composed of a putative leader sequence of 20 residues and the mature enzyme of 122 residues. The cloned lysozyme gene was strongly induced in response to bacterial injection, implying that the enzyme is a part of the immune response of H. cunea. Comparison with other known lysozyme sequences shows that our lysozyme belongs to the chicken lysozyme.

Solubilization of protein-dye complexes on nitrocellulose to quantify proteins spectrophotometrically

Proteins absorbed directly onto nitrocellulose membranes were stained with amido black, ponceau S, colloidal silver, or Coomassie blue and solubilized in dimethyl sulfoxide and the absorbance was measured spectrophotometrically. The optimal wavelength of each dye/protein/nitrocellulose solution was found to be at 625, 529, 420, and 600 nm, respectively. A linear relationship was found between the protein concentration and absorbance at the appropriate wavelength for all the stains with individual purified proteins or protein mixtures. Protein (0.2-0.8 microgram) can be determined with the colloidal silver and 2-30 micrograms with the other stains. Coomassie blue produced variable background staining of the nitrocellulose and is therefore not recommended. Proteins transferred electrophoretically to nitrocellulose from a sodium dodecyl sulfate-polyacrylamide gel were also stained with the above dyes and solubilized in dimethyl sulfoxide. Amido black was the most sensitive stain, detecting proteins in the range of 1-10 micrograms. Components of the gel interfered with silver staining.

The ruminant digestion model using bacteria already employed early in evolution by symbiotic molluscs

The purification and some molecular properties of six lysozymes from the gills of different mytilids and vesicomyids are described: they belong to the previously described Invertebrate lysozyme family. The predominance of the bacterial nutrition in these organisms seems to necessitate the presence of a lysozyme as in the case of the ruminant digestion model.

Characterization of a lysozyme-major histocompatibility complex class II molecule-loading compartment as a specialized recycling endosome in murine B lymphocytes

We have previously identified an intracellular compartment involved in the association between processed lysozyme and IAk major histocompatibility complex class II molecules (called the lysozyme-loading compartment (LLC)). Here, we show that the LLC polypeptide composition analyzed by two-dimensional gel electrophoresis shares similarities with that of early endosomes, but not with that of late endosomes. The transferrin receptor, a well known marker for both early and recycling endosomes, colocalizes with IAk molecules in LLC. Moreover, both transferrin and fluid-phase markers have access to LLC after 15 min of internalization. In the presence of concanamycin B, SDS-stable dimer formation and transport of class II molecules out of LLC are impaired. In contrast, nocodazole treatment has no effect. These results suggest that LLC is a specialized compartment of the recycling pathway involved in lysozyme loading and in the targeting of lysozyme-major histocompatibility class II complexes toward the cell surface.

Monomer concentrations and dimerization constants in crystallizing lysozyme solutions by dialysis kinetics

Dialysis kinetics measurements have been made to study the effect of ionic strength on the dimerization of lysozyme in acidic solutions that lead to the growth of tetragonal lysozyme crystals. Using glutaraldehyde cross-linked dimers of lysozyme, we have determined that both monomers and dimers can escape from 25,000 molecular weight cutoff dialysis membranes with velocity constants of 5.1 x 10(-7) and 1.0 x 10(-7) s(-1) for the monomer and dimer species, respectively. The flux from 25K MWCO membranes has been measured for lysozyme in pH 4.0 buffered solutions of 1, 3, 4, 5, and 7% NaCl over a wide range of protein concentrations. Assuming that dimerization is the first step in crystallization, a simple monomer to dimer equilibrium was used to model the flux rates. Dimerization constants calculated at low protein concentrations were 265, 750, 1212, and 7879 M(-1) for 3, 4, 5, and 7% NaCl, respectively. These values indicate that dimerization increases with the ionic strength of the solution suggesting that aggregation is moderated by electrostatic interactions. At high protein concentrations and high supersaturation, the dimerization model does not describe the data well. However, the Li model that uses a pathway of monomer <-> dimer <-> tetramer <-> octamer <-> 16-mer fits the measured flux data remarkably well suggesting the presence of higher order aggregates in crystallizing solutions.

Application of perfluorocarbons in novel continuous counter-current protein chromatography

In this work the development of a process capable of extracting proteins from particulate-containing solutions (such as fermentation broths) on a continuous basis, and in which absorbent and process streams are contacted counter-currently is described. The process consists of four stages, required for the loading, washing, elution and regeneration of the adsorbent. Because of its counter-current nature, it has improved performance over existing (though not yet commercialized) continuous processes, which have been based on CSTR-type contractors (e.g. PERCAS (McCreath et al., 1993). The improved efficiency has been shown by carrying out extraction of lysozyme from a single component feed stream. The adsorbent used in this work is a Procion Red HE-7B-derivatized perfluorocarbon support, which has shown particular suitability for continuous processes due to its inherently high mechanical strength and high density. Results illustrating yields obtained using this equipment are presented and discussed.

Capillary zone electrophoresis with electrospray condensation particle counting detection

A new sheath flow microelectrospray interface combines capillary electrophoretic separation of protein standards with condensation particle counting detection. Protein separations are performed in both coated and uncoated fused-silica columns. The electrospray needle utilizes a sheath flow rate between 0 and a few microL/min. Typically, the makeup flow is equal to or less than the electroosmotic flow from the separation capillary; thus there is minimal dilution while still providing pH adjustment and solid electrical contact with the separation capillary. While there are some inherent restrictions to a condensation particle counting detector, the microelectrospray needle performs well and has direct application to electrospray mass spectrometry.

Expression and purification of a recombinant metal-binding T4 lysozyme fusion protein

Periplasmic expression of recombinant proteins presents many potential benefits that may aid recovery of the protein product. Muramidases are the preferred agents in effecting selective release of recombinant proteins from the periplasm of E. coli and other Gram negative bacteria. Unfortunately cost restricts the use of pure lytic enzymes at large-scale and their removal as process contaminants adds to later purification demands. We constructed a reusable version of bacteriophage T4 lysozyme, by fusing a His-Gln-(His)3 peptide sequence to the C-terminus of a cysteine-free pseudo wild type bacteriophage T4 lysozyme. The peptide tail allowed rapid and high-level recovery on IDA Sepharose columns charged with Zn2+, Ni2+ and Cu2+ ions. The binding to metal-charged supports was specifically mediated by the histidine-rich tail as no binding was observed for the original cysteine-free pseudo wild type lysozyme. The strength of retention of polyhistidine recombinant T4 lysozyme on charged supports followed the expected Cu > Ni > Zn pattern, but there were few differences in the levels of purity and recovery of the modified enzyme, from columns charged with the different metal ions.

Fractionation of proteins with modified membranes

The fractionation of two proteins, either positively charged (Lysozyme) or negatively charged (bovine serum albumin, BSA) was investigated by varying the ionic strength with unmodified or positively charged inorganic ultrafiltration membranes. Chemical modification was obtained by coating of polyvinylimidazole which amine groups reacted further with bisepoxiranes in order to have both partly quaternized amine group and pH stable network on membrane surface. The retention of the single protein decreases, with ionic strength when electrostatic interactions between the free protein in the bulk and the adsorbed protein onto the membrane are occurring. An increase of single protein retention with modified membranes appears at high ionic strength due to hydrophobic interactions between proteins and polymer coating. For protein mixtures, at low ionic strength (0.015), observed selectivities are more than 10 whatever the membrane used; both membrane fouling and protein-protein interactions occur in the protein mixture. At intermediate (0.25 M) and high (1 M) ionic strengths, the observed selectivity with modified membranes remains stable (about 6) whereas selectively with unmodified membranes decreases and is close to size selectivity. Hence the fractionation of proteins with modified membranes remains satisfactory in the entire range of ionic strengths due to ionic and salt promoted interactions between protein and membranes.

Dimerization of tear lysozyme on hydrophilic contact lens polymers

PURPOSE

Following the solubilization of protein from patient worn soft contact lenses and subsequent analysis via SDS-PAGE, an unidentified 30 kDa protein deposit was commonly observed. The mysterious deposit was found to accumulate on a variety of soft contact lens material.

METHODS

Acuvue, Cibasoft, Excelens and Newvue soft contact lenses were worn by three asymptomatic patients using both daily-wear and extended wear regimens. To characterize the unknown deposit, human tear samples and lens eluted protein were subjected to SDS-PAGE, immunoblotting, enzymatic assays and protein sequencing.

RESULTS

Results show that the 30 kDa protein deposit is the homologous dimer of tear lysozyme. Polymerized lysozyme was found on each of the three lens materials within one h of wear. However, the dimer was not present in the normal tear film.

CONCLUSIONS

Therefore, this dimerization phenomenon is the result of an aggregation and interaction of lysozyme with various soft contact lens polymers.

Correction for amino acid loss during acid hydrolysis of a purified protein

Hydrolyzing a protein in acid for a single hydrolysis interval, normally 24 h, will lead to inaccurate estimates of the amino acid composition of that protein due to an effect of the time of hydrolysis on peptide bond cleavage and amino acid degradation. The simultaneous yield and decay of amino acids during the hydrolysis of a protein can be described by a compartmental model with parameters for the hydrolysis and loss rates specific to each amino acid in a protein. The amino acid composition of the protein prior to hydrolysis can be determined by nonlinear regression of data derived from multiple hydrolysis intervals. In the present study egg-white lysozyme was hydrolyzed in 6 M HCl using 18 hydrolysis intervals (range, 2-141 h) using the conventional duplicate hydrolyses/interval system. Hydrolysis and loss rates were determined for each amino acid. Increasing the number of hydrolysis intervals prior to the maximum point on the hydrolysis curve, and including an hydrolysis interval greater than 100 h increased the accuracy with which the hydrolysis and loss rates were estimated. Most of the amino acids underwent some degree of loss during hydrolysis. Of particular note was the loss rate for cysteic acid, which was greater than that found for serine which is commonly regarded as an acid-labile amino acid. The determined amino acid composition of the protein, based on the nonlinear regression of the data from four different series of hydrolysis intervals, was compared with the known amino acid composition (sequencing). Using the routine duplicate sampling system, a nonlinear regression including 10 hydrolysis intervals (2, 6, 10, 14, 18, 22, 26, 30, 60, and 141 h) resulted in a mean amino acid recovery of 100% (range, 94-110%) and provided an acceptable compromise between accuracy and the cost of analysis.