Fig. 4
From: Structural insights into functional properties of the oxidized form of cytochrome c oxidase
Protonation state of Y244 in the PR (A) and O (B) states. The post translationally modified Y244 forms a H-bonding network with the OH group of the farnesyl side chain of heme a3, a water molecule (W1) and T316. In the PR state, an additional water, W2, is recruited into the heme a3/CuB binuclear center (BNC) to stabilize the tyrosinate configuration of Y244. This water is absent in the O state reported here, as evident in the 2FO-FC electron density map (contoured at 1.0σ) shown in the lower inset, signifying that Y244 is in the neutral protonated state. For clarity the BNC ligands are not shown. The oxygen atom and hydrogen atoms are shown as red and white spheres.
