4OB8: Crystal structure of a novel thermostable esterase from Pseudomonas putida ECU1011

A recombinant carboxylesterase (rPPE) from Pseudomonas putida ECU1011 was previously cloned and engineered to give a potential application for resolving chiral alpha-hydroxy acids including mandelic acids and derivatives. Two variants rPPEW187H and rPPED287A showed a approximately 100-fold increase in activity towards rac-2-acetoxy-2-(2'-chlorophenyl) acetate (rac-AcO-CPA), but rPPED287A had a significant decrease in enantioselectivity (E=8.7) compared to rPPEW187H and the wild-type rPPE (rPPEWT) (E>200). Here we report the crystal structures of rPPEWT and rPPEW187H, both by themselves and in complex with the substrate, to elucidate the structural basis of this phenomenon. An inactive mutation of nucleophile residue S159A was introduced to obtain the structure of rPPES159A/W187H complexed with (S)-AcO-CPA. The structural analysis reveals that the side chain of residue Asp287 in rPPEWT would have a potential steric conflict with (S)-AcO-CPA when the substrate binds at the active site of the enzyme. However, the mutation W187H could facilitate the relocation of Asp287, while D287A directly eliminates the hindrance of Asp287, both of which offer sufficient space for the binding and hydrolysis of substrate. Moreover, Asp287 generates one site of the "three-point attachment model" as a hydrogen-bond donor that determines the excellent enantioselectivity of rPPE in chiral recognition, and D287A would obviously destroy the hydrogen bond and result in the low enantioselectivity of rPPED287A.
PDB ID: 4OB8Download
MMDB ID: 121722
PDB Deposition Date: 2014/1/7
Updated in MMDB: 2017/12
Experimental Method:
x-ray diffraction
Resolution: 1.801  Å
Source Organism:
Similar Structures:
Biological Unit for 4OB8: dimeric; determined by author
Molecular Components in 4OB8
Label Count Molecule
Proteins (2 molecules)
Alpha/beta Hydrolase Fold-3 Domain Protein
Molecule annotation
Chemicals (4 molecules)
* Click molecule labels to explore molecular sequence information.

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