 | Acta Crystallographica Section D Acta Crystallographica Section D BIOLOGICAL CRYSTALLOGRAPHY |
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![[Figure 3]](kw5082fig3mag.jpg)
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Figure 3
ClpB NBD2 K601Q in complex with MANT-dADP. (a) The two different crystal forms obtained for ClpB NBD2. Wild-type protein in complex with ADP, space group P65, is shown in green. Walker A mutant K601Q in complex with MANT-dADP, space group P212121, is shown in blue. The cleft between the core domain and the C-terminal helical bundle is narrowed by 14° in the structure of ClpB NBD2 K601Q in complex with MANT-dADP, leading to a slightly more closed catalytic site. There is a large deviation of the helix–loop–helix motif (710–740), which is owing to different crystal contacts. Furthermore, we observe clear electron density for the previously unstructured pore-loop region. (b) The catalytic site arrangement of ClpB NBD2 K601Q in complex with MANT-dADP. An inorganic phosphate ion is located 5 Å from the β-phosphate of the bound nucleotide, suggesting an ADP + Pi (product-bound) state. The sensor 2 residue Arg806 interacts with the β-phosphate of the nucleotide. The conserved residue Arg621 is located in between the Walker A threonine Thr602 and the Walker B aspartate Asp667 at a position where the essential Mg2+ ion is expected to bind. Distances are given in Å. (c) The MANT group of the fluorescently labelled nucleotide MANT-dADP fills a mainly hydrophobic cavity in ClpB NBD2, explaining the higher binding affinity of MANT-dADP compared with the unlabelled nucleotide ADP. The electrostatic surface potential is visualized (red, negative charge; blue, positive charge). |
![[Figure 3]](kw5082fig3.jpg)
| BIOLOGICAL CRYSTALLOGRAPHY |
ISSN: 1399-0047
