EMP1 (EPO mimetic peptide 1) is disulfide bonded. It is not known if in solution the peptide exists as a dimer. However, in the crystal structure it induces receptor dimerization. Each peptide monomer binds to two receptors, and each receptor binds to each of the two peptides, as shown skematically below.

The peptide was discovered at Affimax by Nick Wrighton and Bill Dower.

Oded Livnah, Enrico A. Stura, Dana L. Johnson, Linda S.Mulcahy, Nicholas C. Wrighton, William J. Dower, Linda K. Jolliffe, and Ian A. Wilson (1996) Functional mimicry of a protein hormone by a peptide agonist: The EPO receptor complex at 2.8Å. Science 273:464-471.
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