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Figure 2
Domain swap in C-DCX. (a) Weighted 2FoFc electron density contoured at 1 r.m.s.d. directly after molecular replacement, prior to refinement. Two search-model protomers (red and blue) without the domain swap (trimmed PDB entry 5ip4) are shown. Continuous electron density starting from residue Lys300 into the opposing protomer at the lower right of the image indicates that the C-terminal 45 residues (Lys300–Asp344) have been swapped. (b) Superposition of the four protomers in the asymmetric unit yields r.m.s.d. values of between 0.5 and 0.9 Å over the entire sequence. Lys300, as the hinge site of the domain swap, is marked for reference. (c) The B-value putty of the asymmetric unit shows that the site of the domain swap does not display the most elevated B values but seems to be rather fixed. Blue and red colours mark the extremes of small and large B values. The termini and a surface loop (marked with an asterisk) display the largest variations in B values. (d) The domain-swapped C-DCX dimer. The surface of one protomer is coloured according to its electrostatic potential and the other is displayed as a ribbon. The view is rotated 90° about the x axis relative to (b) and (c). (e) The same dimer as in (d) with two charged residue pairs shown as stick models. Two globular C-DCX structures (PDB entry 5ip4) are superimposed and shown as grey ribbons. While in the globular structure the residue pairs Lys261/Asp328 and Glu289/Lys307 form charged hydrogen bonds, these interactions are absent in the domain-swapped dimer.

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ISSN: 2059-7983
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