ABSTRACT
A domain-chimeric L-2,3-butanediol dehydrogenase (chimera L-BDH), which was designed to possess both the S-configuration specificity of L-BDH and the stability of meso-BDH, was constructed by exchanging the respective domains of these two BDHs. However, chimera L-BDH possessed a lower enzymatic function than expected based on the two original enzymes. To elucidate the causes of the decreased stability and substrate specificity, crystallization of the protein was performed. Chimera L-BDH was purified to homogeneity via ammonium sulfate fractionation and three column-chromatography steps, and was crystallized using the hanging-drop vapour-diffusion method. The crystals belonged to space group C2221, diffracted synchrotron radiation to 1.58â Å resolution and were most likely to contain two molecules in the asymmetric unit.
Subject(s)
Alcohol Oxidoreductases/chemistry , Crystallization/methods , X-Ray Diffraction/methods , Alcohol Oxidoreductases/metabolism , Escherichia coli/enzymology , Models, Molecular , Protein Conformation , Protein Structure, Tertiary , StereoisomerismABSTRACT
A chimeric (2S, 3S)-butanediol dehydrogenase (cLBDH) was engineered to have the strict (S)-configuration specificity of the (2S, 3S)-BDH (BsLBDH) derived from Brevibacterium saccharolyticum as well as the enzymatic stability of the (2R, 3S)-BDH (KpMBDH) from Klebsiella pneumonia by swapping the domains of two native BDHs. However, while cLBDH possesses the stability, it lacks the specificity. In order to assist in the design a BDH having strict substrate specificity, an X-ray structural analysis of a cLBDH crystal was conducted at 1.58 Å. The results obtained show some readily apparent differences around the active sites of cLBDH and BsLBDH. Based on this structural information, a novel (2S, 3S)-BDH having a preferred specificity was developed by introducing a V254L mutation into cLBDH. The influence of this mutation on the stability of cLBDH was not evaluated. Nevertheless, the technique described herein is an effective method for the production of a tailor-made BDH.
Subject(s)
Alcohol Oxidoreductases/chemistry , Alcohol Oxidoreductases/genetics , Bacterial Proteins/chemistry , Bacterial Proteins/genetics , Corynebacterium/enzymology , Klebsiella/enzymology , Catalytic Domain , Cloning, Molecular , Corynebacterium/chemistry , Corynebacterium/classification , Corynebacterium/genetics , Crystallography, X-Ray , Enzyme Stability , Klebsiella/chemistry , Klebsiella/genetics , Models, Molecular , Mutagenesis, Site-Directed , Structural Homology, Protein , Substrate SpecificityABSTRACT
The development of a stable L-BDH chimera was attempted by exchanging whole domains between two native structural analogs, L-BDH and meso-BDH, because the S-configuration specificity of L-BDH is valuable from the standpoint of its application but its activity is unstable, whereas meso-BDH is stable. The domain chimeras obtained indicated that the leaf-like structures constituting three domains were likely to be mainly associated with chiral recognition, and the fourth domain, the basic domain, is likely to be mainly associated with enzyme stability. A combination of the leaf domains of L-BDH and the basic domain of meso-BDH attained a sufficient level of practical use as an artificial L-BDH chimera, because the resulting enzyme had both stability and S-configuration specificity. However, the levels of stability and specificity were slightly lower than those of the respective enzymes from which they were derived.
