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Figure 1.
Figure 1 Ribbon diagram of the calcium-binding site and
structural changes between calcium-bound (green, chain A) and
calcium-free (cyan, chain B; pink, chain C; tan, chain D) forms
of NA. The loops L1 (245-251), L2 (295-298) and L3 (343-344)
adopt different conformations in the four monomers. In the
calcium-bound form, the protein backbone carbonyl O atoms of
Asp293, Gly297 and Asn347 and the side-chain carboxylate of
Asp324 all bind the calcium cation (yellow sphere). In the
calcium-free form of chain B, the carbonyl groups of Gly297 and
Asn347 are shown to be flipped from the conformation observed in
the calcium-bound form.
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