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. Author manuscript; available in PMC: 2023 Jun 8.
Published in final edited form as: Metallomics. 2019 Jan 23;11(1):85–110. doi: 10.1039/c8mt00221e

Fig. 5.

Fig. 5

Proposed structures of apo-oxytocin and oxytocin with copper or zinc by the Bowers group.172,173 Amino acid residues 1–6 form a 20 membered ring (cyan) closed by a disulfide bond between Cys1 and Cys6 (yellow). Residues 7–9 shown in pink. (A) Left: Chemical structure of biologically active apo-oxytocin. Right: Calculated structure of biologically active apo-oxytocin. (B) Calculated structure of [OT + Zn]2+ showing Zn(II) octahedral coordination to six backbone carbonyl oxygens of residues 2, 3, 4, 6, 8, and 9. Zinc binding may potentiate receptor binding. (C) Lowest energy structure of [OT-3H + Cu]− showing Cu(II) coordination to backbone amide nitrogens of residues 1, 2, 3, and 4. Copper binding neither increases nor decreases oxytocin receptor binding.