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Figure 5.
Figure 5: Electron density at the sites of regulation by
phosphorylation and pH for SoPIP2;1 in its closed conformation.
a, Close-up view of the divalent-cation-binding site showing
the location of the Cd^2+ ion (purple) and the network of
hydrogen bonds linking Gly 30 and Glu 31 through Arg 118 to Arg
190 and Asp 191 of loop D. b, Close-up view of the
phosphorylation residue Ser 115, illustrating its hydrogen bond
to Glu 31. c, Electron density for Ser 274, which contacts Pro
199 and Leu 200 of a neighbouring monomer of the SoPIP2;1
tetramer. Overlaid in grey is the structure of the open
conformation of SoPIP2;1, indicating that a steric clash with
Leu 197 prevents helix 5 from adopting this conformation when
Ser 274 is dephosphorylated. d, Close-up view of His 193. When
protonated, an alternative conformation for His 193 (grey) may
be adopted that forms a salt bridge to Asp 28. All 2F[o] - F[c]
maps are contoured at 1.0  .
Numbers are distances in Å.
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