Crystal structure of ADP/AMP complex of Escherichia coli adenylate kinase

Introduction.Adenylate kinases (AKs, ATP:AMP phosphotransferase, EC 2.7.4.3) are a family of enzymes which catalyze the following reaction: Mg 2ϩ ATP ϩ AMP 7 Mg 2ϩ ADP ϩ ADP.Several structural works have revealed that AKs have two highly flexible domains which close over bound substrates. 1 The LID domain covers ATP and the site of phosphoryl transfer and the AMP-binding domain closes on AMP when it is bound.Key residues to the domain closure and substrate binding are conserved five arginines in the active site.In Escherichia coli AK, they are Arg36, Arg88, Arg123, Arg156, and Arg167.A previous mutational study suggested an important role of Arg156 in catalysis 2 but its function is not well defined although two E. coli AK structures were already solved with P 1 ,P 5 -di(adenosine 5Ј)-pentaphosphate (Ap 5 A) and ␤-␥-imidoadenosine 5Ј-triphosphate (AMPPNP)/AMP, respectively.3,4 Here, we report the crystal structure of E. coli AK with bound ADP and AMP determined at a resolution of 2.8 Å and propose possible roles of Arg156 in substrate binding and catalysis.