Crystal structure of biphalin sulfate:
a multireceptor opioid peptide
by
Flippen-Anderson JL, Deschamps JR,
George C, Hruby VJ, Misicka A, Lipkowski AW.
Laboratory for the Structure of Matter,
Naval Research Laboratory,
Washington, DC 20375-5000, USA.
flippen@harker.nrl.navy.mil
J Pept Res 2002 Mar;59(3):123-33

ABSTRACT

Biphalin is a dimeric opioid peptide, composed of two tetrapeptides connected 'tail-to-tail', that exhibits a high affinity for all three opioid receptor types (i.e. mu, delta and kappa). This study presents the X-ray crystal structure of biphalin sulfate and compares it to other opioids that interact with the same biological targets. Both halves of the molecule have a folded backbone conformation but differ significantly from one another. Residues 1-4 in biphalin, which compare well with the delta selective opioid peptide DADLE, fold into a random coil. Residues 5-8, which can be fit to the mu selective peptide D-TIPP-NH2, exhibit a fairly normal type III' beta bend. Biphalin also exhibits structural similarities with two naltrexone analogs, naltrexonazine and norbinaltorphamine, that are specific to mu and kappa receptor sites.

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