Purification and characterization of lysozyme from hemolymph of Heliothis virescens larvae

Lysozyme is an important antibacterial protein in the insect defense system. Lysozyme was isolated from hemolymph of Heliothis virescens larvae using gel filtration and ion-exchange chromatography. Heliothis lysozyme had a molecular mass of 16,000 daltons by SDS-PAGE. Using acid gel electrophoresis, Heliothis lysozyme migrated faster than egg white lysozyme. The pI of Heliothis lysozyme was estimated as greater than 9.5. Heliothis lysozyme had specific bactericidal activity against three Gram-positive bacteria but no activity against Escherichia coli. The bactericidal activity was stable at 100 degrees C at pH 3.0 after 60 min incubation, but was labile at 100 degrees C at pH 6.8 after 60 min incubation. Heliothis lysozyme was an inducible protein that increased 9 times when comparing unvaccinated with vaccinated larvae. Lysozyme from H. virescens was more similar in molecular mass, heat sensitivity and pH sensitivity to lysozyme isolated from Galleria mellonella and Bombyx mori than to lysozyme isolated from Hyalophora cecropia.

Mixed dimers formed by crosslinking of native and glycated proteins in the absence of free sugar

After a hyperglycaemic episode, glycated proteins remain in the body until removed by protein turnover. We have shown that in the absence of free sugar, such proteins can crosslink to native proteins, forming mixed dimers. They can also induce native proteins to crosslink into homodimers, presumably by release of a soluble crosslinking agent. Similar reactions in vivo could be responsible for the deposition of serum proteins in diabetic kidney, nerve and other tissues. Exposure to glycating sugar for brief periods, or a low concentration, still produced glycated protein capable of crosslinking to other proteins under sugar-free conditions. These crosslinks are nonfluorescent, unlike the advanced glycation endproducts usually observed.

Separation of proteins of nearly the same size but having different isoelectric points by convective electrophoresis

A method for separating proteins of nearly the same size but having different isoelectric points is presented. The method used is convective electrophoresis, which is based on the simultaneous effects of diffusion, electrical migration and opposing convective flow on the transport of proteins through a porous membrane. The pairs of model proteins used in this study were cytochrome c-lysozyme and human serum albumin-haemoglobin. The obtained results show that with a careful adjustment of pH these proteins can be separated by a continuous manner, and no coupling of protein fluxes could be detected in either case.

Application of immobilized metal ion chelate complexes as pseudocation exchange adsorbents for protein separation

The interactions of horse muscle myoglobin (MYO), tuna heart cytochrome c (CYT), and hen egg white lysozyme (LYS) with three different immobilized metal ion affinity (IMAC) adsorbents involving the chelated complexes of the hard Lewis metal ions Al3+, Ca2+, Fe3+, and Yb3+ and the borderline Lewis metal ion Cu2+ have been investigated in the presence of low- and high-ionic strength buffers and at two different pH values. In contrast to the selectivity behavior noted with buffers of high ionic strength, with low-ionic strength buffers, these three proteins interact with the hard metal ion IMAC adsorbents in a manner more characteristic of cation exchange behavior, although in contrast to the cation exchange chromatography of these proteins, as the pH value of the elution buffer was increased, the retention also increased. The selectivity differences observed under these conditions appear to be due to the formation of hydrolytic complexes of these immobilized metal ion chelate systems involving a change in the coordination geometry of the im-M(n+)-chelate at higher pH values. The experimental observations have been evaluated in terms of the effective charge on the immobilized metal ion chelate complex and the charge characteristics of the specific proteins.

Simple two-step procedure for the preparation of highly active pure equine milk lysozyme

A fast, simple two-step purification scheme is presented for the isolation of lysozyme at a high yield from equine milk. In the first step, fluidized bed technology, using the Streamline system, was exploited. In the following step, advantage was taken of Ca(2+)-induced conformational changes to obtain a pure, high specific activity, enzyme fraction by hydrophobic interaction chromatography.

Characterization of seven basic endochitinases isolated from cell cultures of Citrus sinensis (L.)

Seven endochitinases (EC 3.2.1.14) (relative molecular masses 23,000-28,000 and isoelectric points 10.3-10.4) were purified from nonembryogenic Citrus sinensis L. Osbeck cv. Valencia callus tissue. The basic chitinase/lysozyme from this tissue (BCLVC) exhibited lysozyme, chitinase and chitosanase activities and was determined to be a class III chitinase. While BCLVC acted as a lysozyme at pH 4.5 and low ionic strength (0.03) it acted as a chitinase/chitosanase at high ionic strengths (0.2) with a pH optimum of ca. 5. The lysozyme activity of BCLVC was inhibited by histamine, imidazole, histidine and the N-acetyl-D-glucosamine oligosaccharide (GlcNAc)3. The basic chitinase from cv. Valencia callus, BCVC-2, had an N-terminal amino acid sequence similar to tomato and tobacco AP24 proteins. The sequences of the other five chitinases were N-terminal blocked. Whereas BCLVC was capable of hydrolyzing 13.8-100% acetylated chitosans and (GlcNAc)4-6 oligosaccharides, BCVC-2 hydrolyzed only 100% acetylated chitosan, and the remaining enzymes expressed varying degrees of hydrolytic capabilities. Experiments with (GlcNAc)2-6 suggest that BCLVC hydrolysis occurs in largely tetrasaccharide units whereas hydrolysis by the other chitinases occurs in disaccharide units. Cross-reactivities of the purified proteins with antibodies for a potato leaf chitinase (AbPLC), BCLVC, BCVC-3, and tomato AP24 indicate that these are separate and distinct proteins.

Kinetically trapped structure in the renaturation of reduced oxindolealanine 62 lysozyme

The refolded products of reduced native lysozyme and reduced OX62 lysozyme, in which Trp62 is converted to oxindolealanine (OX62) during the renaturation of sulfhydryl-disulfide interchange reactions at pH 8 and 37 degrees C, were investigated. On gel-chromatography eluted with 10% aqueous acetic acid containing 4 M urea, two peaks appeared in the refolded product of reduced OX62 lysozyme while a single peak appeared in the refolded product of reduced native lysozyme. From the analyses of the activity and primary and the tertiary structures of the derivative, the structure of the derivative from reduced native lysozyme was confirmed to be identical to that of the untreated one. On the other hand, the refolded product from reduced OX62 lysozyme had the same primary structure but a different tertiary structure compared to the untreated one. The tertiary structure of the refolded product from the reduced OX62 lysozyme was changed to that of the untreated one by the denaturation-renaturation treatment under nonreduced conditions. However, the refolded species was barely changed to that of the untreated one by incubation under physiological conditions. Therefore, the refolded product from reduced OX62 lysozyme was suggested to be a metastable and kinetically trapped product in the renaturation process of reduced OX62 lysozyme. In addition, an interaction involving the folding process of reduced lysozyme was discussed on the basis of the NMR analyses of the metastable structure.

The effects of filtration on protein nucleation in different growth media

Filtration effects of turkey egg white lysozyme solution (TEWL) prior to subjecting it to crystallization conditions are investigated. Filtering TEWL solution and crystallizing it in ungelled media significantly decreased the number of conditions yielding crystals. This decrease dependent on the membrane cut-off used for filtration. From this, the postulated factors aiding in nucleation are estimated to be 0.17 microns in diameter. The existence of these factors was verified by the procedure of reversed filtration: filtered solutions passed through their inverted filter membrane a second time lead to improved crystallization results. The effect of aging of the TEWL solution prior to subjecting it to ungelled crystallization conditions was also verified. We did not find any time-dependent change in the size or the number of crystals per drop. Repeating the filtration experiments in agarose-gelled crystallization media showed that the influence of filtration on the crystallization outcome was significantly diminished. Far better crystallization results were obtained compared to ungelled media. However, there is a certain aging effect linked to filtration in gelled media. Different crystallization results were obtained depending on whether filtration was performed before or after aging and subsequent crystallization. This suggests a secondary time-dependent effect.

One of the rubber latex allergens is a lysozyme

BACKGROUND

Type I hypersensitivity reactions caused by latex products are ascribed to proteins eluted from them, but little is known about the properties of these allergenic proteins. The reason for the cross-reaction between rubber latex and fruits is also not known. We have speculated that a series of defense-related proteins in plants is a cause of latex allergy and the cross reaction.

OBJECTIVE

To verify our hypothesis, we selected a lysozyme as a representative defense-related protein and examined its relationship to latex allergy.

METHODS

Lysozymes eluted from latex gloves were detected with a cell-suspension clearing test. A chromatographically separated lysozyme was investigated for its physicochemical and enzymatic properties and allergenicity.

RESULTS

Lysozyme activity was detected in extracts from ammoniated latex and latex gloves. We separated a lysozyme (27 kd; isoelectric point, 9.5) using cation-exchange and gel filtration chromatography. This lysozyme was enzymatically very similar to fruit lysozymes and was demonstrated to be an allergen.

CONCLUSIONS

One of the rubber latex allergens is a lysozyme that has similarities to fruit lysozymes. This suggests the relevance of defense-related proteins to latex allergy and the cross reaction.

Genetic and biochemical characterization of the Lactobacillus delbrueckii subsp. lactis bacteriophage LL-H lysin

LL-H, a virulent phage of Lactobacillus delbrueckii subsp. lactis, produces a peptidoglycan-degrading enzyme, Mur, that is effective on L. delbrueckii, Lactobacillus acidophilus, Lactobacillus helveticus, and Pediococcus damnosus cell walls. In this study, the LL-H gene mur was cloned into Escherichia coli, its nucleotide sequence was determined, and the enzyme produced in E. coli was purified and biochemically characterized. Mur was purified 112-fold by means of ammonium sulfate precipitation and cation-exchange chromatography. The cell wall-hydrolyzing activity was found to be associated with a 34-kDa protein. The C-terminal domain of Mur is not essential for catalytic activity since it can be removed without destroying the lytic activity. The N-terminal sequence of the purified lysin was identical to that deduced from the nucleotide sequence, but the first methionine is absent from the mature protein. The N-terminal part of this 297-amino-acid protein had homology with several Chalaropsis-type lysozymes. Reduction of purified and Mur-digested L. delbrueckii cell wall material with labeled NaB3H4 indicated that the enzyme is a muramidase. The temperature optimum of purified Mur is between 30 and 40 degrees C, and the pH optimum is around 5.0. The LL-H lysin Mur is stable at temperatures below 60 degrees C.

Bacteriolytic activities of the free-living soil amoebae, Acanthamoeba castellanii, Acanthamoeba polyphaga and Hartmannella vermiformis

Bacteriolytic activities of axenically grown free-living soil amoebae Acanthamoeba castellanii, Acanthamoeba polyphaga and Hartmannella vermiformis towards various Gram-positive and Gram-negative bacteria were determined. A spectrophotometric assay revealed that the specific bacteriolytic activities of both Acanthamoeba species were higher as those of the three Hartmannella strains. Bacillus megaterium, Bacillus subtilis, Chromatium vinosum, Micrococcus luteus and Pseudomonas fluorescens were more easily lysed than the other bacteria tested. Agrobacterium tumefaciens, Klebsiella aerogenes and Serratia marcescens were hardly affected at all by the amoebal bacteriolytic activities. Among the Gram-negative bacteria we observed differences in lysis sensitivity while the Gram-positive bacteria tested were sensitive to lysis. Isoelectric focusing (IEF) gel-electrophoresis in the pH range 3-10 was performed to separate the bacteriolytic isoenzymes of amoebae. Bacteriolytic patterns were shown by using an activity assay in which lysis bands were formed in the agar/bacteria gel-overlay. The activity assay revealed remarkable differences in typical banding patterns for bacteriolytic activities among amoebae. Distinct differences between typical pI points of bacteriolytic activities in Acanthamoeba and Hartmannella were shown. Bacteriolytic activities of Hartmannella were more pronounced and observed in the isoelectric points (pI) range of 4.0-9.3 while for Acanthamoeba the range was pI 4.5-8.9.

Purification of recombinant human basic fibroblast growth factor: stability of selective sorbents under cleaning in place conditions

Human basic fibroblast growth factor (bFGF) was produced from recombinant Escherichia coli by high-cell-density cultivation. In order to develop a purification strategy for large-scale purification, chromatographic sorbents with different anionic functional groups were compared in terms of selectivity for bFGF and stability under cleaning in place (CIP) conditions. Heparin-Sepharose CL-6B, Fractogel EMD-SO3- 650 (S) and SP-Sepharose (high performance) were found suitable for this purpose with decreasing selectivity in that order. Each sorbent was treated eight times under CIP conditions employing both 0.2 and 1.0 M NaOH, in order to study modifications of these sorbents. Heparin-Sepharose displayed more than 50% loss of capacity after the first CIP treatment and decreasing selectivity with each cycle. Both cation exchangers displayed almost constant results regarding selectivity and capacity. The Fractogel EMD-SO3- exhibited only slightly lower selectivity for bFGF than Heparin-Sepharose and the highest capacity of all sorbents tested. Agglomeration of bFGF at low salt concentrations was a serious problem. By direct application of pooled fractions from Fractogel EMD-SO3- onto Heparin-Sepharose a highly pure product was obtained; however, the recovery after Heparin-Sepharose was only 30%.

Insect lysozyme from house fly (Musca domestica) larvae: possible digestive function based on sequence and enzymatic properties

Lysozyme was purified from the homogenate of the whole body of house fly (Musca domestica) larvae by standard chromatographic techniques. The purified lysozyme was sequenced and its enzymatic properties were examined. This lysozyme was a chicken-type lysozyme composed of 122 amino acids, showing about 75% identity with fruit fly lysozymes and 38% with human lysozyme. This enzyme was inactive towards Micrococcus luteus and under the physiological conditions of PH 7.0 and ionic strength 0.1, but was as active toward glycol chitin as was hen lysozyme. The pH-dependent profile of lytic activity towards M. luteus showed that house fly lysozyme has an acidic pH optimum and shows no enzymatic activity above Ph 7. These features are analogous with those of ruminant stomach lysozymes which have evolved for the digestive function, suggesting that this lysozyme does not function as a self-defense protein, like hen and human lysozyme, but as a digestive enzyme, probably in the gut of the insect body. Although a similar functional conversion to digestive enzyme was reported in fruit fly, phylogenetic tree analysis indicates that the evolutionary change of lysozyme to a digestive enzyme occurred similarly in fruit fly and house fly, but the events are not related and occurred independently in each strain. This observation is in contrast with the case of ruminant stomach lysozymes, which were recruited before the divergence of each species of ruminants.

Electrophoretic polymorphism in rabbit tear lysozyme

Rabbit tears were found to contain two lysozymes which differed in their electrophoretic mobility and were designated tear lysozymes 1 and 2. Rabbit tear lysozyme 1 was purified to homogeneity by conventional purification methods. It was found to be distinct from other known mammalian c-type lysozymes, rabbit tear lysozyme 2 and the major rabbit gastrointestinal lysozyme. The activity profile is centered around the neutral region with an optimum of 7 which is slightly lower than that for chicken lysozyme. The thermal stability as well as inhibition profiles by the substrate analogues, N-acetylglucosamine (NAG) and chitotetraose (NAG)4 are comparable to those of chicken lysozyme. Based on its molecular weight and catalytic properties this isozyme is classified as a c-type lysozyme.

Analysis of some operating parameters of novel adsorbents for recovery of proteins in expanded beds

We have analysed some operational parameters for two novel adsorbents intended for recovery of proteins from particle-containing feedstocks using expanded bed adsorption. The adsorbents tested were STREAMLINE DEAE and STREAMLINE SP, ion exchangers based on an agarose/crystalline quartz composite. Parameters analysed included bed expansion, adsorption efficiency, washing and elution. Bed expansion was considerably lower for STREAMLINE adsorbents compared to conventional agarose based media, higher flow velocities were thus possible during the expanded bed process. Breakthrough capacity was 63 mg ml-1 for lysozyme on STREAMLINE SP and 36 mg ml-1 for bovine serum albumin on STREAMLINE DEAE at a flow velocity of 300 cm h-1. To achieve high breakthrough capacity, the sedimented bed height should be at least 10 cm. Furthermore, breakthrough capacity increased to some extent when temperature was increased from room temperature to 36 degrees C, a phenomenon which can be useful in some processes. The number of living E. coli cells in the effluent was reduced by a factor of 10(5) after washing with 15 sedimented bed volumes. The optimal flow velocity for elution was 100 cm h-1 considering time for elution and volume of the eluted fraction. Flow direction during elution in packed bed mode had little impact on the elution volume, however, elution in expanded bed mode increased the volume by approx. 40%. The data presented on the performance of STREAMLINE adsorbents show that they are very useful for recovery of proteins from particle-containing feedstocks using expanded bed adsorption.

A possible role of ER-60 protease in the degradation of misfolded proteins in the endoplasmic reticulum

Wild-type human lysozyme (hLZM) is secreted when expressed in mouse L cells, whereas misfolded mutant hLZMs are retained and eventually degraded in a pre-Golgi compartment (Omura, F., Otsu, M., Yoshimori, T., Tashiro, Y., and Kikuchi, M. (1992) Eur. J. Biochem. 210, 591-599). These misfolded mutant hLZMs are associated with protein disulfide isomerase (Otsu, M., Omura, F., Yoshimori, T., and Kikuchi, M. (1994) J. Biol. Chem. 269, 6874-6877). From the observation that this degradation is sensitive to cysteine protease inhibitors, such as N-acetyl-leucyl-leucyl-norleucinal and N-acetyl-leucyl-leucyl-methioninal, but not to the serine protease inhibitors, 1-chloro-3-tosylamido-7-amino-2-heptanone and (p-amidinophenyl)methanesulfonyl fluoride, it was suggested that some cysteine proteases are likely responsible for the degradation of abnormal proteins in the endoplasmic reticulum (ER). ER-60 protease (ER-60), an ER resident protein with cysteine protease activity (Urade, R., Nasu, M., Moriyama, T., Wada, K., and Kito, M. (1992) J. Biol. Chem. 267, 15152-15159), was found to associate with misfolded hLZMs, but not with the wild-type protein, in mouse L cells. Furthermore, denatured hLZM is degraded by ER-60 in vitro, whereas native hLZM is not. These results suggest that ER-60 could be a component of the proteolytic machinery for the degradation of misfolded mutant hLZMs in the ER.

Computation of the electrophoretic mobility of proteins

A scheme is presented for computing the electrophoretic mobility of proteins in free solution, accounting for the details of the protein shape and charge distribution. The method of Teubner is implemented using a boundary integral formulation within which the velocity distribution, the equilibrium electrical potential around the molecule, and the potential distribution due to the applied field are solved for numerically using the boundary element method. Good agreement of the numerical result is obtained for spheres with the corresponding semi-analytical specialization of Henry's analysis. For protein systems, the method is applied to lysozyme and ribonuclease A. In both cases, the predicted mobility tensors are fairly isotropic, with the resulting scalar mobilities being significantly smaller than for spheres of equal volume and net charge. Comparisons with previously published experimental results for ribonuclease show agreement to be excellent in the presence of a net charge, but poorer at the point of zero charge. The approach may be useful for evaluating approximate methods for estimating protein electrophoretic mobilities and for using electrophoretic measurements to obtain insight into charge distributions on proteins.

Investigations of the interactions of saccharides with the lysozyme from bacteriophage lambda

The bacteriophage lambda R gene has been isolated into an Escherichia coli expression system and the R gene product, a lysozyme, has been overexpressed and purified to homogeneity using an efficient purification procedure. A turbidimetric assay utilizing chloroform-treated E. coli cells has been optimized to assess the bacteriolytic activity of the purified enzyme. Using this assay, oligomers of beta (1 --> 4) N-acetyl-D-glucosamine at high concentrations were shown to inhibit lysozyme but were not cleaved by the enzyme. Differential scanning calorimetry revealed that the thermal denaturation of lysozyme was found to increase in the presence of (GlcNAc)3 and (GlcNAc)5. The lysozyme was also expressed in an E. coli strain auxotrophic for methionine, allowing for the incorporation of [methyl-13C]methionine into the enzyme. An alteration of the [1H-13C]HMQC NMR spectra of the labelled enzyme was observed in the presence of (GlcNAc)5. Commercially available nitrophenyl glycosides did not act as substrates for lambda lysozyme. The results indicate that lambda lysozyme has specific interactions with oligosaccharides of N-acetylglucosamine, but is incapable of hydrolyzing these sugars. The relevance of the structure of peptidoglycan to the activity of lambda lysozyme is discussed.

Isolation of hen egg white lysozyme, ovotransferrin and ovalbumin, using a quaternary ammonium bound to a highly crosslinked agarose matrix

A single-step anion-exchange chromatographic separation of egg white proteins was carried out using a Q Sepharose Fast Flow column. The separation resulted in the isolation of two lysozyme peaks with purities of ca. 99 and 88%, one peak of ovotransferrin purified to ca. 75% and two ovalbumin peaks with purities of ca. 54 and 98%. Recoveries were estimated to be ca. 60, 100 and 83% for lysozyme, ovotransferrin and ovalbumin, respectively. The amino acid compositions of all collected peaks have also been determined. This confirmed the identity of some of the proteins contained in these peaks.

Effective renaturation of reduced lysozyme by gentle removal of urea

To increase the folding yield of concentrated reduced lysozyme, we developed a renaturation method by means of dialysis from concentrated urea with redox agents. After lysozyme was incubated in the reducing buffer (8 M urea solution) with oxidized glutathione, renaturation of reduced lysozyme was started by dialysis against the dialyzing buffer containing 8 M urea with redox agents. The urea concentration of the dialyzing bottle was gradually diluted with dialyzing buffer without urea at a flow rate of 0.1 ml/min by high pressure pump. Using this systematic dialysis, a concentration as high as 5 mg/ml of reduced lysozyme could be renaturated in 80% yield, while the folding yield was < 5% even at a concentration of 1 mg/ml using a conventional rapid dilution method [Goldberg et al. (1991) Biochemistry, 30, 2790-2797]. Therefore, it was concluded that gentle removal of urea from denatured proteins, dissolved in concentrated urea solution, by means of dialysis should be useful to renature denatured proteins effectively.

Purification of egg-white allergens

Purification procedures for the four egg-white proteins ovomucoid, ovotransferrin, ovalbumin, and lysozyme are presented with reference to mechanistic studies at epitope levels of allergic reactions to these proteins. The applied procedures resulted in four preparations containing less than 0.1% contaminating proteins each. The purified protein preparations were characterized by SDS-PAGE and by crossed immunoelectrophoresis with polyclonal antibodies raised against an egg-white extract or the purified proteins. The necessity of these well-characterized proteins in studies on allergic reactions was shown by testing human sera in immunoblots of lysozyme, and by immunoblots of ovomucoid probing with antibodies against the proteins.