Title
Structural basis for an atypical active site of an l‐aspartate/glutamate‐specific racemase from Escherichia coli
Author
Jae-Woo Ahn, Jeong Ho Chang, Kyung-Jin Kim
Year
2015
Journal
FEBS Letters
Abstract
We determined the crystal structure of EcL‐DER to elucidate protein function and substrate specificity. Unlike other asp/glu racemases, EcL‐DER has an unbalanced pair of catalytic residues, Thr83/Cys197, at the active site that is crucial for l‐ to d‐unidirectional racemase activity. EcL‐DER exhibited racemase activity for both l‐glutamate and l‐aspartate, but had threefold higher activity for l‐glutamate. Based on the structure of the EcL‐DERC197S mutant in complex with l‐glutamate, we determined the binding mode of the l‐glutamate substrate in EcL‐DER and provide a structural basis for how the protein utilizes l‐glutamate as a main substrate. The unidirectionality, despite an equilibrium constant of unity, can be understood in terms of the Haldane relationship.
Instrument
J-1500
Keywords
Circular dichroism, Stereochemistry, Biochemistry