Homology models of <i>So</i>CMO1 and <i>So</i>CMO2 proteins.

(A) Cartoon representation of the SoCMO2 trimer with each subunit in a different color; the close-up shows the residues involved in iron coordination in the Rieske center (Cys162, His164, Cys181, His184) and in the non-heme mononuclear iron (His287, His292, Asp398), as well as the aspartate residue involved in the transfer of electrons between the two iron centers (Asp283). (B) Cartoon representation of aligned SoCMO1 (pink) and SoCMO2 (green) monomers. In panels A and B, carbon atoms are colored in pink (SoCMO1) or green (SoCMO2), oxygen atoms in red and nitrogen atoms in blue and iron and sulfur atoms are shown as spheres colored orange and yellow, respectively. (C) Cartoon representation of the modeled SoCMO2A active site showing a choline molecule (black carbon atoms) docked into it. The choline trimethylammonium group is in a favorable position to interact with the aromatic box formed by residues Tyr281, Tyr295, Phe301, as well as with the near Asp346 residue. The choline hydroxyl group is oriented towards the iron atom as needed to establish a coordination bond with it. (D) Cartoon representation of the modeled SoCMO1 active site, showing the putative active site residues at position equivalent to the ones in the SoCMO2 model. (E) Sequence logos of selected positions of CMO1 and CMO2 proteins showing the conservation of residues putatively involved in choline binding in CMO2. Residue conservation is shown as probability. The amino acids color scheme of the logos is according to their chemical properties: polar (S, N), green; aromatic (Y, F), purple; acidic (E), red; and hydrophobic (L, M), black. Residue numbers correspond to the complete SoCMO2 sequence (XP_021849509) or to the complete SoCMO1 sequence (XP_021866412), as appropriate.