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![[Figure 3]](dw5208fig3mag.jpg)
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Figure 3
Conformational changes in ClpC1-NTD crystallographic structures. (a) Superposition of the complexes of ClpC1-NTD with ECU (protein, beige; ECU site 1, blue; ECU site 2, purple) and RUF-I (protein and RUF-I both shown in green). Subtle changes are seen at the peptide-binding site, with a domain movement of helices 4–5 and 8–9 caused by a twist in the 70s loop. RUF-I occupies the cyclic portion of ECU site 2. (b) The N-terminus of ClpC1-NTD-L92S/L96P is curved in approximately the same position as in apo ClpC1-NTD and the complexes with RUF-I and CYMA. A distortion of helix 6 is observed just before L96P. (c) R.m.s.d. of Cα atons compared with apo ClpC1-NTD (PDB entry 3wdb). There is very little movement of the backbone between the apo and RUF-I-bound forms. However, there are substantial movements of the termini, the repeat-linking 70s loop and helices 4–5 and 8–9. (d) Close-up view of the unusual conformation of the N-terminus of ClpC1-NTD (Met1-Phe2-Glu3-Arg4); ClpC1-NTD-L92S/L96P is in purple, ClpC1-NTD–RUF-I is in green and ClpC1-NTD–ECU is in beige. Arg4 undergoes a substantial conformational change when compared with the unbound structure in the ClpC1-NTD-L92S/L96P mutant, allowing it to hydrogen-bond (red line) from the Arg4 NH2 group to the carbonyl of Ser92. Arg4 O hydrogen-bonds to Ile103 N in the loop following helix 6 in all three structures. In addition, Arg4 N hydrogen-bonds to Met1 O in the ClpC1-NTD–RUF-I complex. |
![[Figure 3]](dw5208fig3.jpg)
 | STRUCTURAL BIOLOGY |
ISSN: 2059-7983
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