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. 2017 Jan 5;7:39674. doi: 10.1038/srep39674

Figure 5. The ATP-binding sites.

Figure 5

The conformations of the known signature motifs for ATP binding in ASKHA domains, ADENOSINE (GxxPGP), PHOSPHATE 1 (DxGGTxDDT) and PHOSPHATE 2 (DVGGT) highlighted in brown, are strictly conserved in Apcα and Apcα′, as well as in Acxα and Hydα. (a) Superimposed structures of the ATP and substrate binding sites of pantothenate kinase (gray) and Apcα (orange). Apcα is in an open state. The architecture of the ATP binding site is well conserved, although, in addition, loop segments α406–α417 and α691–α692 from a two-helix protrusion of the ASHKA module and from the C-terminal domain of Apcα, respectively, contribute to form the ATP binding site in Apcα. The predicted substrate binding site of Apcα is formed by the loop α279–α281 at the N-terminus of helix α282:α289, segment α333–α334 and Leuα345 of the central β-strand and helix α79:α87 (highlighted in blue). (b) Superimposed structures of the ATP and substrate binding sites of pantothenate kinase and Apcα′. The ATP binding site of Apcα′ (green) is in a closed state. The predicted substrate binding site is primarily formed segment α′70–α′77, the N-terminal loop of helix α′251:α′265 and the segment α′275–α′282. ADP is shown in a ball-and-stick representation (carbon in gray). The 2Fobs − Fcalc electron density (brown) of ADP is drawn at a contour level of 0.9 σ.