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Figure 4
Potential side-entry sodium ion binding site found just outside of the SF. (a) 2Fo−Fc electron density map contoured at 1σ shown as a blue mesh. Coordination distances to a putative sodium ion (cyan sphere) are given in Ångstroms. The Asp66(A) residue comes from the A polypeptide, whereas the Asp66(B) residue comes from the B polypeptide. (b) The position of the potential side entry sodium ion binding site is shown, the a polypeptide subunit is shown as a yellow cartoon while the a polypeptide subunit is shown as an orange cartoon. Potassium and sodium ions are shown as purple and cyan spheres, respectively.

IUCrJ
Volume 8| Part 3| May 2021| Pages 421-430
ISSN: 2052-2525
https://doi.org/10.1107/S205225252100213X