FIGURE 1.

Overview of APSK nucleotide binding and structure. A, schematic of ordered and random nucleotide binding proposed for APSK from P. chrysogenum and E. coli, respectively. B, structural overview of AtAPSK and nucleotide binding sites. The ribbon diagram of AtAPSK (24) shows the core α/β-nucleotide binding domain (rose and blue in each monomer of the dimer) and the smaller active site capping domain (gray). APS (green) and ATP (yellow) bound in their respective nucleotide binding sites are shown in each active site of the dimer. Residues of the P-loop are shown as a space-filling model (red). The position of the N-terminal α-helix is indicated by the letter N.