Large-scale purification of halophilic enzymes by salting-out mediated chromatography

A tribute to Dr. Serge N. Timasheff, our mentor

Dr. Serge N. Timasheff, our mentor and friend, passed away in 2019. This article is a collection of tributes from his postdoctoral fellows, friends, and daughter, who all have been associated with or influenced by him or his research. Dr. Timasheff is a pioneer of research on thermodynamic linkage between ligand interaction and macromolecular reaction. We all learned a great deal from Dr. Timasheff, not only about science but also about life.

Alternative downstream processes for production of antibodies and antibody fragments

Protein-A or Protein-L affinity chromatography and virus inactivation are key processes for the manufacturing of therapeutic antibodies and antibody fragments. These two processes often involve exposure of therapeutic proteins to denaturing low pH conditions. Antibodies have been shown to undergo conformational changes at low pH, which can lead to irreversible damages on the final product. Here, we review alternative downstream approaches that can reduce the degree of low pH exposure and consequently damaged product. We and others have been developing technologies that minimize or eliminate such low pH processes. We here cover facilitated elution of antibodies using arginine in Protein-A and Protein-G affinity chromatography, a more positively charged amidated Protein-A, two Protein-A mimetics (MEP and Mabsorbent), mixed-mode and steric exclusion chromatography, and finally enhanced virus inactivation by solvents containing arginine. This article is part of a Special Issue entitled: Recent advances in molecular engineering of antibody.

Characterization and subunit structure of the ATP synthase of the halophilic archaeon Haloferax volcanii and organization of the ATP synthase genes

The archaeal ATPase of the halophile Haloferax volcanii synthesizes ATP at the expense of a proton gradient, as shown by sensitivity to the uncoupler carboxyl cyanide p-trifluoromethoxyphenylhydrazone, to the ionophore nigericin, and to the proton channel-modifying reagent N,N'-dicyclohexylcarbodiimide. The conditions for an optimally active ATP synthase have been determined. We were able to purify the enzyme complex and to identify the larger subunits with antisera raised against synthetic peptides. To identify additional subunits of this enzyme complex, we cloned and sequenced a gene cluster encoding five hydrophilic subunits of the A1 part of the proton-translocating archaeal ATP synthase. Initiation, termination, and ribosome-binding sequences as well as the result of a single transcript suggest that the ATPase genes are organized in an operon. The calculated molecular masses of the deduced gene products are 22. 0 kDa (subunit D), 38.7 kDa (subunit C), 11.6 kDa (subunit E), 52.0 kDa (subunit B), and 64.5 kDa (subunit A). The described operon contains genes in the order D, C, E, B, and A; it contains no gene for the hydrophobic, so-called proteolipid (subunit c, the proton-conducting subunit of the A0 part). This subunit has been isolated and purified; its molecular mass as deduced by SDS-polyacrylamide gel electrophoresis is 9.7 kDa.

Analysis of pH-dependent protein interactions with gel filtration medium

A prepacked Superose 12 HR 10/30 column was used to study the effects of elution ionic strength and pH on the chromatographic behaviour of a strong hydrophobic Clostridium thermocellum endoglucanase (1) and two weak hydrophobic proteins, Clostridium thermocellum endoglucanase C and egg white lysozyme. Ion-exclusion or ion-exchange interactions between weakly hydrophobic proteins and the gel matrix were observed at low ionic strength, depending on whether the pH of the elution buffer was higher or lower than the pI values of the proteins. These interactions were due to the presence of negatively charged groups on the surface of Superose and could be eliminated at any pH by adding electrolyte at a concentration determined by its chemical identity. The optimum results were observed with sodium sulphate at a concentration of 100 mM. The chromatographic behaviour of strong hydrophobic endoglucanase (1) on a Superose column as a function of pH was much more complex because of two interplaying effects, electrostatic and hydrophobic. Ideal size-exclusion chromatography could be achieved only in a narrow range of the conditions: first, the mobile phase must contain a weak salting-out electrolyte such as NaCl, and second, the mobile phase pH must be high enough that hydrophobic interactions between the solute and support are balanced by their electrostatic repulsion. At pH greater than pI, the retardation of endoglucanase (1) gradually increased with decreasing pH as a result of lowering of repulsive electrostatic interactions whether or not the buffer ionic strength was high. At pH less than pI a drastic increase in the capacity factor k' was observed owing to the additivity of hydrophobic and ion-exchange effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Arginine deiminase from Halobacterium salinarium. Purification and properties

Arginine deiminase from the extreme halophilic archaebacterium Halobacterium salinarium was purified to homogeneity in a four-step procedure with a 310-fold enrichment. The enzyme consists of two identical subunits of 55 kDa; its native molecular mass is 105 kDa. The pI of 4.7 indicates that acidic nature of the protein, which is evidenced by its amino acid composition, which shows an excess of more than 15% of acidic amino acids. The N-terminal amino acid of the enzyme is lysine. Arginine deiminase from Halobacterium salinarium exhibits its highest catalytic activity in the presence of 3.5 M-NaCl, pH 7.6, and at 40 degrees C. The half-activity constant, Ks, for arginine is 3.1 mM. The enzyme is inhibited by ornithine.

The novel disulfide reductase bis-gamma-glutamylcystine reductase and dihydrolipoamide dehydrogenase from Halobacterium halobium: purification by immobilized-metal-ion affinity chromatography and properties of the enzymes

An NADPH-specific disulfide reductase that is active with bis-gamma-glutamylcystine has been purified 1,900-fold from Halobacterium halobium to yield a homogeneous preparation of the enzyme. Purification of this novel reductase, designated bis-gamma-glutamylcystine reductase (GCR), and purification of halobacterial dihydrolipoamide dehydrogenase (DLD) were accomplished with the aid of immobilized-metal-ion affinity chromatography in high-salt buffers. Chromatography of GCR on immobilized Cu2+ resin in buffer containing 1.23 M (NH4)2SO4 and on immobilized Ni2+ resin in buffer containing 4.0 M NaCl together effected a 120-fold increase in purity. Native GCR was found to be a dimeric flavoprotein of Mr 122,000 and to be more stable to heat when in buffer of very high ionic strength. DLD was chromatographed on columns of immobilized Cu2+ resin in buffer containing NaCl and in buffer containing (NH4)2SO4, the elution of DLD differing markedly in the two buffers. Purified DLD was found to be a heat-stable, dimeric flavoprotein of Mr 120,000 and to be very specific for NAD. The utility of immobilized-metal-ion affinity chromatography for the purification of halobacterial enzymes and the likely cellular function of GCR are discussed.

Superoxide dismutase from the extremely halophilic archaebacterium Halobacterium cutirubrum

Halobacterium cutirubrum, a member of the archaebacteria, contains one superoxide dismutase (EC 1.15.1.1). This enzyme functions in the high-ionic-strength intracellular environment and protects the organism against the toxic effects of the superoxide anion. The enzyme has been purified to about 90% homogeneity by a four-step procedure which never removes it from conditions of high ionic strength. The subunits of the purified enzyme have a molecular weight of 25,000 and are possibly in tetrameric association. The enzyme shows anomalously high resistance to azide inhibition and sensitivity to inactivation by hydrogen peroxide. Metal analysis indicates 0.2 atom of Mn, less than 0.03 atom of Cu, and less than 0.001 atom of Fe per subunit. The low content of Mn may explain the low specific activity found for this enzyme compared with that of eubacterial enzymes. Optimum activity occurs in 2 M KCl; KCl gives about twice as much activity as NaCl over the range of 2 to 4 M. The enzyme appears to be related to those isolated from other archaebacteria but also exhibits several novel features.

Thermodynamic analysis of the effect of concentrated salts on protein interaction with hydrophobic and polysaccharide columns

An attempt was made to explain the effect of concentrated salts on protein interaction with hydrophobic columns. From the previously observed results of preferential interactions for salting-out salts with proteins, it was shown that the free energy of the protein is increased by addition of the salts and this unfavorable free energy is smaller for the proteins bound to the columns because of their smaller surface area exposed to solvent; i.e., the bound form of the proteins is thermodynamically more stable. This explains the protein binding to the hydrophobic columns at high salt concentrations and the elution by decreasing the salt concentration. The unfavorable interaction free energy was greater for Na2SO4 or (NH4)2SO4 than for NaCl, which explains the stronger effect of the former salts on the protein binding to the columns. The observed favorable interaction between KSCN or guanidine hydrochloride and the proteins explains the decreasing effect of these salts on the protein binding to the hydrophobic columns.

Automated purification of human erythrocytic 6-phosphogluconate dehydrogenase

Human 6-phosphogluconate dehydrogenase (6PGD) was purified from hemolyzate by group affinity chromatography on 2',5'-ADP-Sepharose, followed by buffer exchange chromatography on Sephadex G-25 and finally salting-out chromatography on Sepharose 6B. An apparatus was assembled from commercially available elements, in which the purification procedure can proceed and be completed unattended and under fully automatic control. The weekly production of the set-up is at present 10 mg of pure 6PGD. The choice of the purification of procedure and the advantages of automation are discussed.