Figure 3.
Comparison of the conserved steroid binding sites near the K path entrance of CcO. (A) Detailed binding interactions between the deoxycholate and residues in RsCcO (subunit I, green; subunit II, cyan), including those that comprise the K path. Dochl and DM are shown as sticks and colored the same as in Figure 2. Residues that interact with the dochl molecule are shown in sticks and colored by atom type. Cd is shown as a wheat sphere. Part of the hydroxyl farnesyl tail of heme a3 is shown as purple sticks. (B) Comparison of the binding of the steroid molecules between RsCcO and bovine CcO. Subunits I and II of both structures are represented in the same way as in panel A. Subunit VIa from a neighboring CcO molecule in the bovine CcO structure is colored wheat. Dochl resolved in the RsCcO structure is shown as red sticks. The cholate molecule (chl) found in the bovine CcO structure is shown in sticks and colored by atom type (blue and red). Part of the phosphatidylethanolamine molecule (PE) resolved in the bovine CcO structure is shown as yellow sticks. Some residues from both structures that interact with the steroid molecule are shown as sticks. The structure of RsCcO with dochl is labeled in black, while that of bovine CcO with chl is labeled in blue.