Structural basis for an atypical active site of an <scp>l</scp>‐aspartate/glutamate‐specific racemase from <i>Escherichia coli</i>
抄録
<jats:p>We determined the crystal structure of <jats:italic>Ec</jats:italic>L‐DER to elucidate protein function and substrate specificity. Unlike other asp/glu racemases, <jats:italic>Ec</jats:italic>L‐DER has an unbalanced pair of catalytic residues, Thr83/Cys197, at the active site that is crucial for <jats:sc>l</jats:sc>‐ to <jats:sc>d</jats:sc>‐unidirectional racemase activity. <jats:italic>Ec</jats:italic>L‐DER exhibited racemase activity for both <jats:sc>l</jats:sc>‐glutamate and <jats:sc>l</jats:sc>‐aspartate, but had threefold higher activity for <jats:sc>l</jats:sc>‐glutamate. Based on the structure of the <jats:italic>Ec</jats:italic>L‐DER<jats:sup>C197S</jats:sup> mutant in complex with <jats:sc>l</jats:sc>‐glutamate, we determined the binding mode of the <jats:sc>l</jats:sc>‐glutamate substrate in <jats:italic>Ec</jats:italic>L‐DER and provide a structural basis for how the protein utilizes <jats:sc>l</jats:sc>‐glutamate as a main substrate. The unidirectionality, despite an equilibrium constant of unity, can be understood in terms of the Haldane relationship.</jats:p>
収録刊行物
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- FEBS Letters
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FEBS Letters 589 (24PartB), 3842-3847, 2015-11-07
Wiley