Expression and purification of polyhistidine-tagged firefly luciferase in insect cells--a potential alternative for process scale-up

Spectroscopic and functional characterization of Lampyris turkestanicus luciferase: a comparative study

Functional expression and spectroscopic analysis of luciferases from Lampyris turkestanicus and Photinus pyralis were carried out. cDNA encoding L. turkestanicus luciferase was isolated by reverse transcription-polymerase chain reaction, cloned, and functionally expressed in Escherichia coli. The luciferases were purified to homogeneity using Ni-nitrilotriacetic acid Sepharose, and kinetic properties of luciferase from L. turkestanicus were compared with that from P. pyralis. Amino acid differences in its primary structures in relation to P. pyralis luciferase brought about changes in the kinetic properties of the enzyme as evidenced by substantial lowering of Km for ATP, increased light decay time, and decreased thermostability. Luciferase from L. turkestanicus was used to carry out Michaelis-Menten kinetics with a Km of 95.5 muM for ATP and 20 muM for luciferin. Maximum activity was recorded at pH 8.5, so it might be a suitable reporter for microbial screening at alkaline pH. Tryptophan fluorescence for P. pyralis luciferase was higher than L. turkestanicus luciferase. Substitution of some residues in L. turkestanicus luciferase appears to change the kinetic properties by inducing a substantial tertiary structural change, without a large effect on secondary structural elements, as revealed by intrinsic and extrinsic fluorescence, Fourier transform infrared spectroscopy, and near-ultraviolet circular dichroism spectra.

Mutagenesis of solvent-exposed amino acids in Photinus pyralis luciferase improves thermostability and pH-tolerance

Firefly luciferase catalyses a two-step reaction, using ATP-Mg2+, firefly luciferin and molecular oxygen as substrates, leading to the efficient emission of yellow-green light. We report the identification of novel luciferase mutants which combine improved pH-tolerance and thermostability and that retain the specific activity of the wild-type enzyme. These were identified by the mutagenesis of solvent-exposed non-conserved hydrophobic amino acids to hydrophilic residues in Photinus pyralis firefly luciferase followed by in vivo activity screening. Mutants F14R, L35Q, V182K, I232K and F465R were found to be the preferred substitutions at the respective positions. The effects of these amino acid replacements are additive, since combination of the five substitutions produced an enzyme with greatly improved pH-tolerance and stability up to 45 degrees C. All mutants, including the mutant with all five substitutions, showed neither a decrease in specific activity relative to the recombinant wild-type enzyme, nor any substantial differences in kinetic constants. It is envisaged that the combined mutant will be superior to wild-type luciferase for many in vitro and in vivo applications.

Expanded bed adsorption for purification of alcohol dehydrogenase using a dye-iminodiacetic acid matrix

Expanded bed adsorption (EBA) was successfully applied for the purification of alcohol dehydrogenase (ADH) from unclarified bakers' yeast homogenate using a new dye-iminodiacetic acid (IDA) matrix carrying immobilized metal ions. The existence of cells and cell debris do not have a significant effect on the adsorption of ADH on the matrix. The presence of imidazole in adsorption buffer was found to be an important factor in reducing the level of the adsorbed contaminant proteins. The optimal imidazole concentration was 5 mM. The dynamic binding capacity of the dye-IDA matrix in EBA was found to be 569 U/ml matrix. A chromatography of one-step elution with imidazole was developed, in which ADH was successfully adsorbed in the presence of 5 mM imidazole; subsequently, the column was washed with 5 mM imidazole containing 1 M NaCl and eluted with 150 mM imidazole containing 1.5 M NaCl. The purification factor and ADH recovery were 8.8 and 93.5%, respectively.

Development of new dye-metal agarose-coated alumina matrix and elution strategy for purification of alcohol dehydrogenase

A high-density matrix was prepared by coating an alumina particle with agarose using an emulsion technique. Iminodiacetic acid and Cibacron Blue 3GA were immobilized onto this matrix. Charging this matrix with zinc created a useful chromatography matrix for purification of yeast alcohol dehydrogenase. The elution strategy was then investigated to obtain a high recovery of this enzyme and a high purification factor. One-step elution using 4 mM EDTA containing 0.5 M NaCl resulted in 66% enzyme recovery and a purification factor of 4.7. Two-step elution using imidazole containing NaCl resulted in a higher purification factor. The first-step elution using 5 mM imidazole containing 1 M NaCl released most contaminant proteins. The second-step elution using 150 mM imidazole containing 1.5 M NaCl resulted in high-performance purification with a purification factor of 6.5 and an enzyme recovery of 40.7%. Equilibration of the matrix with imidazole prior to sample application increased the purification factor and the enzyme recovery to 8.4 and 76.8%, respectively.

Integrated strategy for selective expanded bed ion-exchange adsorption and site-specific protein processing using gene fusion technology

The highly charged domain Z(basic) can be used as a fusion partner to enhance adsorption of target proteins to cation exchanging resins at high pH-values. In this paper, we describe a strategy for purification of target proteins fused to Z(basic) at a constant physiological pH using cation exchange chromatography in an expanded bed mode. We show that two proteins, Klenow DNA polymerase and the viral protease 3C, can be efficiently purified from unclarified Escherichia coli homogenates in a single step with a selectivity analogous to what is normally achieved by affinity chromatography. The strategy also includes an integrated site-specific removal of the Z(basic) purification handle to yield a free target protein.