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Figure 7
Variation of the GluB13 conformation with pH. (a) Overlay of ten cubic insulin structures from pH 5.0 to 9.0. The residues that undergo major structural changes are highlighted. The arrows indicate the trend upon pH increase. (b1) Six GluB13 residues in the T6 hexamer form a highly ordered hydrogen-bond network with neighboring water molecules. (b2) In the [{\rm T}_{3}{\rm R}^{\rm f}_{3}] hexamer three of the GluB13 residues exhibit double conformations, while the other three are retracted away from the hexamer core. (c1) At pH 5.0, the two GluB13 residues of the cubic polymorph are hydrogen-bonded (proximal conformation). (c2) At pH 9.0, the GluB13 residues in the cubic polymorph have completely switched to a new conformation that considerably separates them (distant conformation). (d) In the polycrystalline cubic structure the two GluB13 residues are found in the distant conformation. Structures are colored based on pH. PDB codes are shown in parentheses.

Journal logoSTRUCTURAL
ISSN: 2059-7983
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