Expression of the murine leukemia virus protease in fusion with maltose-binding protein in Escherichia coli

The protease of murine leukemia virus (MLV) was cloned into pMal-c2 vector, expressed in fusion with maltose-binding protein (MBP), and purified to homogeneity after Factor Xa cleavage of the chimeric protein. Substantial degradation of the fusion protein was observed during expression, which severely diminished the yield. The degree of degradation of the fusion protein was even more pronounced when a single-chain form of the MLV protease was cloned after the gene coding for MBP. To increase the yield, a hexahistidine tag with an additional Factor Xa cleavage site was cloned after the protease and nickel chelate affinity chromatography was used as the first purification step. The modified procedure resulted in substantially higher yield as compared to the original procedure. The degradation of hexahistidine-tagged active site mutant MLV protease was very low and comparable to that obtained with hexahistidine-tagged MBP, but purified MLV protease alone was not able to degrade purified MBP, suggesting that during expression the active MLV protease may activate bacterial proteases which appear to be responsible for the degradation of the fusion proteins.     

Purification of interleukin-1 beta converting enzyme, the protease that cleaves the interleukin-1 beta precursor.

We have purified the IL-1 beta converting enzyme from the THP-1 cell line using standard chromatographic techniques and obtained the N-terminal amino acid sequence of this novel protein. After stimulation of THP-1 cells with lipopolysaccharide, hydroxyurea, and silica, the protease was solubilized by multiple freeze/thawing. The protein was purified by ion-exchange chromatography, affinity chromatography on blue agarose, gel filtration, and chromatofocusing. The molecular weight of the protein is approximately 22,000 Da and the pI is between 7.1 and 6.8. The overall yield for this procedure was 16% of the activity found in the initial cell lysates. An antiserum raised against a peptide based on the N-terminus was used to precipitate the protease, confirming our identification of the 22,000-Da protein as the IL-1 beta converting enzyme.     

Purification and Characterization of Vibrio vulnificus Protease

A protease was purified from a strain of Vibrio vulnificus isolated from the blood of a septicemic human. The vibrio was cultured in bacto peptone-yeast extract medium, and the protease was purified by a purification procedure including ultrafiltration of the culture supernatant with an Amicon YM 5 membrane, diethylaminoethyl-Sephacel column chromatography, Sephacryl S-200 column chromatography and fast protein liquid chromatography on Mono Q column. The protease preparation revealed homogeneity on polyacrylamide gel electrophoresis and about 30,000-fold purification was achieved, with a yield of about 30%. The isoelectric point of the purified V. vulnificus protease was about 5.80 and its molecular weight was ca. 45,000 by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The optimum pH of the protease activity was 8.0. The V. vulnificus protease was inhibited by a metalloprotease inhibitor and zinc ion and/or ferrous ion were essential for its enzyme activity. No cysteine residue was detected in the V. vulnificus protease. The protease had caseinolytic, elastolytic and collagenolytic activities.     

Purification and characterization of the mouse mammary tumor virus protease expressed in Escherichia coli.

The mouse mammary tumor virus (MMTV) protease gene was cloned into pGEX-2T, an Escherichia coli expression vector containing the glutathione S-transferase coding region of Schistosoma japonicum. The chimeric protein was formed by fusion of the glutathione S-transferase with a hexapeptide which contains a thrombin cleavage site, followed by the MMTV protease. Affinity chromatography on a glutathione-Sepharose 4B column was used to isolate the chimeric protein. After thrombin cleavage, the glutathione S-transferase and the protease were separated by gel filtration chromatography on a Sephadex G-75 column. The overall yield of the protease purification procedure was about 1 mg of protease/liter of culture, and the specific activity was 380 pmol/min.micrograms of enzyme. Like other retroviral proteases, the MMTV enzyme was active as a dimer, showed maximum activity at pH between 4 and 6, and could be inhibited by pepstatin A and a phosphinic acid derivative HIV-1 protease inhibitor. Enzymatic characterization of this protease reveals its broad specificity, showing a clear preference for the oligopeptide substrate mimicking the cleavage site at the amino-terminal end of the capsid protein (kcat/Km = 9725.5 M-1.s-1). The chimeric protein was also an active dimer and showed a similar Km (17 microM) for such an oligopeptide, although its kcat was about 10 times smaller. Autocatalytic processing of the MMTV protease was observed after expression of clones containing the natural cleavage site, as it occurs at the amino-terminal end of the viral protease, instead of the thrombin-sensitive sequence.     

Purification and partial characterization of a Nocardia brasiliensis extracellular protease.

Nocardia brasiliensis possess proteolytic activities that can be readily detected in a variety of media. In a modified formulation of a growth medium originally used for Streptomyces aureofaciens, N. brasiliensis was found to secrete proteolytic enzymes, one of which was capable of hydrolyzing casein. This enzyme was purified to homogeneity from cell-free culture filtrates of N. brasiliensis. The purification procedure included ion-exchange chromatography on carboxymethyl-Sepharose, gel filtration on Sephadex G-100, and affinity chromatography, using a hemoglobin-Sepharose resin. The molecular weight of the N. brasiliensis protease was found to be 25,000 by gel filtration and 35,000 by sodium dodecyl sulfate-discontinuous gel electrophoresis. The enzyme is inhibited by o-phenanthroline and 8-hydroxyquinoline-5-sulfonic acid but is not affected by EDTA. Average values for its kinetic parameters were 0.288 mumol of hemoglobin solubilized per min per mg of enzyme for Vmax and 0.76 mM for Km, using hemoglobin as the substrate.     

Synthesis of 18-substituted steroids Part II (1). Improvements in the preparation of 18-hydroxyprogesterone.

18-Hydroxyprogesterone is conveniently prepared from 3beta-acetoxypregn-5-en-20beta-ol by a modified route. 3beta-Acetoxy-18-iodopregn-5-en-20-one, obtained by the hypoiodite-photolysis procedure and oxidation, is treated with methanolic silver acetate to give the 18, 20-epoxy-20-methoxy derivative, which crystallises directly without need for chromatography. Hydrolysis of the 3-acetate, and a modified Oppenauer oxidation, gave 18-hydroxy-progesterone in 24% over-all yield.     

Purification and partial characterization of poliovirus protease 2A by means of a functional assay.

The purification of poliovirus protease 2A from infected cells by a functional assay is described. A small synthetic peptide was cleaved specifically by an esterase present in poliovirus-infected cells. Since the enzyme proved extremely unstable in crude extracts a rapid and efficient purification procedure had to be developed. By treatment with different detergents followed by high-speed centrifugation, the esterase activity was separated from inactivating cellular enzymes and was solubilized. Purification to more than 90% homogeneity could be achieved by a single chromatography step, namely, by gel filtration through Superose 12 under fast-protein liquid chromatography conditions. The esterase activity was associated with a protein of 17,000 daltons and copurified with poliovirus protein 2A. Furthermore, antibodies to 2A specifically precipitated the esterase activity. Thus, the esterase was identified as poliovirus protease 2A. Inhibition studies with known protease inhibitors revealed that 2A is probably a sulfhydryl protease. Of the metal ions tested, only zinc exerted significant inhibitory effects. The esterase activity was optimal near neutral pH and had an extremely short half-life at physiological temperatures.     

Double-headed protease inhibitors from black-eyed peas. I. Purification of two new protease inhibitors and the endogenous protease by affinity chromatography.

Two new double-headed protease inhibitors have been isolated from black-eyed peas. The isoinhibitors can be purified to homogeneity with greater than 90% recovery in a four-step procedure by means of sequential affinity chromatography on trypsin-Sepharose and chymotrypsin-Sepharose affinity columns. The isoinhibitors both have molecular weights near 8,000 and both have the same NH1-terminal residue serine. Black-eyed pea chymotrypsin and trypsin inhibitor (BEPCI) has an isoelectric point of 5.1 and inhibits trypsin and chymotrypsin simultaneously. Black-eyed pea trypsin inhibitor (BEPTI) has an isoelectric point of 6.5 and inhibits 2 molecules of trypsin simultaneously. BEPTI binds to chymotrypsin-Sepharose above pH 6 but does not inhibit chymotrypsin in the standard inhibitor assay with 10-3 M substrate. These new inhibitors are distinct from the Ventura inhibitor isolated from Serido black-eyed peas. An endogenous seed protease has been isolated from black-eyed peas by affinity chromatography on soybean inhibitor-carboxymethylcellulose affinity columns. A protease-BEPCI complex has been isolated by ion exchange chromatography. A dual physiological function of inhibition and protection of the seed protease is suggested as a plausible role of seed protease inhibitors.     

Purification of plasminogen activator from Rous sarcoma virus-infected chick embryo fibroblast culture medium

A new procedure for the purification of plasminogen activator secreted by cultured Rous sarcoma virus-infected chick embryo fibroblasts was described. The enzyme was isolated from culture medium containing 0.75% calf serum depleted of plasminogen by lysine-agarose affinity column chromatography and of high-molecular-weight protease inhibitors by ultracentrifugation. The culture conditions allowed convenient preparation of large amounts of culture fluid with relatively high concentrations of plasminogen activator. The purification of the enzyme was accomplished by affinity chromatography on fibrin-celite and p-aminobenzamidine-agarose columns, and by gel-filtration chromatography in the presence of urea. The activity was recovered in greater than 90% yield, and the enzyme was essentially homogeneous when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Yields from 500 ml culture fluid exceeded 500 micrograms.     

Amphibian embryo protease inhibitors. IV. Studies on an inhibitor of chymotrypsin and papain

Amphibian embryo chymotrypsin and papain inhibitor (ACPI) purified by the procedure described in this paper produces a single band on sodium dodecyl sulfate (SDS) gel electrophoresis and a single peak on Sephadex G-75 chromatography. Except for its enzyme specificity, ACPI is very similar to amphibian embryo trypsin inhibitor (ATI). Its molecular weight is about 10,500 and its amino acid composition is typical of many naturally occurring protease inhibitors. Inhibition develops slowly, is retarded by the presence of substrate and is temporary. ACPI is localized in the yolk platelets and its disappearance both from whole embryos and from select tissue types corresponds closely with that of ATI. Possible roles for amphibian embryo proteases and protease inhibitors in development are discussed.     

Purification and properties of human kidney-cortex hexosaminidases A and B.

Hexosaminidases (EC 3.2.1.30) A and B from human kidney cortex were purified to homogeneity by using concanavalin A affinity chromatography, ion-exchange chromatography and gel filtration. The yield of homogeneous isoenzymes improved approx. 20-fold, giving preparations of hexosaminidases A and B with specific activities of about 200 and 325 units/mg of protein respectively. The kinetic and structural properties of kidney hexosaminidase isoenzymes were studied and compared with the hexosaminidase isoenzymes from human placenta. The amino acid composition of hexosaminidase A was significantly different from that of hexosaminidase B. In the event of success in developing enzyme-replacement therapy for Tay-Sachs and Sandhoff's diseases, this modified procedure can furnish larger amounts of homogeneous isoenzymes.     

The purification of alpha 1-antichymotrypsin from human serum using DNA-cellulose chromatography

By exploiting its capacity for binding to DNA, the protease inhibitor alpha 1-antichymotrypsin has been isolated from human serum by ammonium sulfate fractionation and successive chromatography on QAE-Sephadex, DNA-cellulose, and Sephacryl S-300. This experimental procedure compares favorably with existing methods for preparing alpha 1-antichymotrypsin in terms of overall yield and practical convenience. The purified alpha 1-antichymotrypsin was homogeneous as judged by electrophoretic and immunoelectrophoretic criteria. From its inhibition of the fluorimetric titration of chymotrypsin with 4-methylumbelliferyl-p-trimethylammonium cinnamate it was shown to combine with chymotrypsin in a 1:1 molar ratio and thus to retain its biological activity.     

Affinity purification of HIV-1 and HIV-2 proteases from recombinant E. coli strains using pepstatin-agarose

A procedure is described which employs pepstatin-agarose for the affinity purification of either HIV-1 or HIV-2 protease from two similar recombinant E. coli constructs that were developed for the expression of these enzymes. HIV-2 protease was routinely expressed at much higher levels than the HIV-1 enzyme and pepstatin-agarose was the only chromatography step required to isolate pure HIV-2 protease from crude bacterial lysates. A Mono S ionic exchange step following pepstatin-agarose chromatography was sufficient to bring the HIV-1 protease to homogeneity. Purification of either enzyme can be completed in several days yielding homogeneous preparations suitable for crystallization and other physical characterization.     

Purification to homogeneity of a neutral metalloproteinase from Streptomyces caespitosus

We established an improved purification procedure for Streptomyces caespitosus neutral protease (ScNP) from culture supernatants of S. caespitosus. The procedure comprises sequential ammonium sulfate fractionation and column chromatography procedures with anion exchange chromatography, followed by hydrophobic-interaction chromatography and gel filtration. Purified ScNP revealed a single band with a molecular mass of 14 kDa by SDS-PAGE under reduced conditions and did not contain any detectable pigment, which has not been completely removed by other methods. We also purified another protease with a molecular mass of 40 kDa from the culture supernatants. The pure preparation of ScNP obtained by this procedure is suitable for spectrophotometric measurement of its catalytic activity.     

Expression and purification of human PYY(3-36) in Escherichia coli using a His-tagged small ubiquitin-like modifier fusion

Human PYY(3-36) (hPYY3-36) is a 34 amino acid hormone that has received a great deal of attention due to its effects on appetite regulation. hPYY(3-36) was modified at the N-terminus with an octahistidine tag and factor Xa protease sequence along with the small ubiquitin-like modifier (SUMO) tag and expressed in Escherichia coli. The protein was purified from clarified E. coli lysate by immobilized metal affinity chromatography (IMAC) with a yield of 30±7mg/L of induced culture returned as an average over seven runs, and its identity was confirmed by Western blot and hPYY antibody recognition. The SUMO-tagged hPYY(3-36) was digested with two different proteases to return either His-tagged hPYY(3-36) or unmodified hPYY(3-36): (1) digestion with SUMO protease proceeded at about 50% efficiency yielding His-tagged hPYY(3-36); (2) digestion with factor Xa protease proceeded at greater than 90% efficiency yielding final hPYY(3-36). Products were purified from the digestion mixtures by reverse-phase high-performance liquid chromatography (C(18)) or IMAC, respectively, the identities were confirmed by mass spectrometry and hPYY antibody recognition, and the folded state of His-tagged hPYY(3-36) was investigated by circular dichroism spectroscopy.     

Purification and characterization of a secreted protease from the pathogenic marine bacterium Vibrio anguillarum

Vibrio anguillarum is a pathogenic marine bacterium which causes the disease vibriosis in salmonid fish, which is characterized by a fatal hemorrhagic septicemia accompanied by massive tissue destruction. In this paper, the purification of the major caseinolytic extracellular protease from V. anguillarum is presented. The purification steps include ammonium sulfate precipitation, DEAE-Sepharose chromatography, Sephacryl S-200 chromatography, and DEAE high-pressure liquid chromatography. The purified protease migrates with Mr = 38,000 upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A slightly larger protease of Mr 40,000 is also separated by this procedure, but accounts for only a minor fraction of the caseinolytic activity. The Mr 38,000 protease displays a broad pH activity profile in the neutral to basic range. It is not inhibited by serine, cysteine, or acid protease inhibitors, but is inhibited by EDTA and 1,10-phenanthroline, suggesting that it is a metalloprotease. The activity of the EDTA-inactivated protease could be partially restored by the addition of Ca2+ and Zn2+ together. The molecular weight and inhibition data show some similarities with proteases isolated from other Vibrio species such as Vibrio cholerae and Vibrio vulnificus.     

Multiple proteases from Streptomyces moderatus: I. Isolation and purification of five extracellular proteases

The presence of multiple proteases in the culture filtrate of Streptomyces moderatus was detected. After preliminary purification by ammonium sulfate precipitation and decolorization using DEAE-cellulose, the fractionation of various proteases was carried out using CM-trisacryl cation-exchange chromatography. By this procedure, four different protease fractions (Fr.) were separated (Fr. I, II, III, and IV). The first fraction was further separated into two different proteolytically active fractions (Fr. Ia and Fr. Ib) by DEAE-trisacryl anion-exchange chromatography. Fraction Ia was purified further by affinity chromatography on N-carbobenzoxy-d-phenylalanyl triethylenetetramine-Sepharose 4B. The second fraction (Fr. Ib) was purified by gel filtration on Ultrogel AcA 44. For the purification of the other protease fractions (Fr. II, III, and IV) single-step affinity chromatography methods were employed. Protease fractions II and III were purified by ϵ-aminocaproyl-4-(4-aminophenylazo)phenylarsonic acid Sepharose 4B and protease fraction IV was purified on ϵ-aminocaproyl trialanine-Sepharose 4B. All five proteases purified were found to be apparently homogeneous by gel electrophoretic methods.     

High molecular weight glycosylated protease in calf brain. Purification and partial characterization

A high molecular weight protease has been purified to homogeneity from calf brain cytosol. The purification procedure involves ammonium sulfate fractionation of the cytosol followed by chromatography on DEAE-Sephacel, hydroxylapatite, concanavalin A-Sepharose 4B and Sephacryl S-300. The molecular weight of the native protease was estimated to be Mr = 465,000 by high pressure liquid chromatography. It is composed of a closely moving doublet of Mr = 165,000 and 155,000, as determined on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. It degrades [methyl-14C] alpha-casein with a broad pH optimum of 6.8-8.5. [methyl-14C]bovine serum albumin and 125I-bovine serum albumin are hydrolyzed to the same extent as [methyl-14C]alpha-casein, whereas [methyl-14C]methemoglobin is hydrolyzed to half the extent of [methyl-14C] alpha-casein. Divalent cations, nucleotides, and known protease inhibitors (phenylmethylsulfonyl fluoride, p-chloromercuribenzoate, iodoacetic acid, N-ethylmaleimide, leupeptin, antipain, pepstatin, and hemin) have no effect on the activity of the protease. The protease is glycosylated and appears to aggregate readily. Aggregation may be reversed by treating the protease with certain organic solvents. The protease seems to maintain full activity after heat treatment. Electron microscopic data reveals a spherical structure of 20-nm diameter.     

Chemical synthesis of a biotinylated derivative of the simian immunodeficiency virus protease. Purification by avidin affinity chromatography and autocatalytic activation.

The protease from simian immunodeficiency virus (SIV) was chemically synthesized by automated solid-phase technology as an NH2-terminally extended derivative, capped with biotin. Biotin-linker-(SIV protease (1-99)): the linker segment, Gly-Gly-Asp-Arg-Gly-Phe-Ala-Ala, corresponds to the amino acid sequence preceding that of the protease in the SIV gag/pol precursor polyprotein. Accordingly, the Ala-Pro bond joining the octapeptide linker to the protease constitutes a site naturally cleaved by the protease during viral maturation. This strategy for synthesis was designed to facilitate purification of the biotinylated protein derivative from a complex mixture of reaction products by avidin/agarose-affinity chromatography and to provide the means for autocatalytic removal of the biotin-linker segment. As anticipated, folding of the full-length construct leads to activation of the enzyme and excision of the desired 99-residue SIV protease (overall yield, approximately). The specificity of the synthetic SIV protease toward a number of well characterized protein substrates was the same as observed for the nearly identical enzyme from human immunodeficiency virus type 2 (HIV-2 protease) and distinct from that of the more disparate HIV-1 protease. The same functional ordering with respect to the human retroviral proteases was reflected in Ki values observed with a number of protease inhibitors. Thus, the folded synthetic SIV protease shows patterns of specificity and susceptibility to inhibition that are in accord with what would be expected based upon its degree of structural similarity to proteases from HIV-1 and HIV-2.     

Purification of prosthetically intact sulfite oxidase from chicken liver using a modified procedure

A modified procedure was used to purify sulfite oxidase (sulfite:O2 oxidoreductase; EC 1.8.3.1) from chicken liver in high yield. The modifications included dialysis of the enzyme against a buffered solution containing sodium molybdate (prior to ion-exchange chromatography), which apparently reconstituted any demolybdo enzyme present in the extract, and phenyl-Sepharose column chromatography. Analysis showed that the purified enzyme contained Mo and heme in a 1.03:1.00 ratio, indicating that the enzyme was prosthetically intact; exogenous heme and other colored proteins were absent from the final pool. Treatment of the sulfite-reduced enzyme with 50 mM cyanide at pH 8.5 resulted in a gradual loss of catalytic activity with a half-life of 19.7 min. Analysis of the cyanide-inactivated enzyme gave a Mo:heme ratio of 1.02:1.00, providing the first direct evidence that the enzyme does not lose molybdenum when inactivated with cyanide. This modified purification procedure provides enzyme in high yield which is well-suited for experiments requiring prosthetically intact enzyme and which is not contaminated with extraneous heme or with other redox active proteins.