Patterns of product inhibition for bacterial nitrite reductase |
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Authors: | R Dhesi R Timkovich |
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Affiliation: | 1. National Institutes of Health, NICHD, Bethesda, MD 20205 USA;2. Department of Chemistry, University of Georgia, Athens, GA 30602 USA |
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Abstract: | PO +Dehydrophenylalanine (delta Phe) having the E-configuration (delta EPhe ; phenyl and C = O cis) was incorporated into [Leu5]-enkephalin in order to restrict its conformation. Compared with the Z-isomer, in the radio-ligand receptor binding assays, [D-Ala2, delta EPhe4 , Leu5] enkephalin showed drastically decreased potency for the delta and mu opiate receptors, i.e., 260- and 150-fold loss of affinity, respectively. The results strongly indicate that the opiate receptors require the Z-configuration (phenyl and C = O, trans) of the delta Phe4 residue and may require a specific interrelationship between the aromatic rings of the Tyr1 and Phe4 residues in the molecule for binding. The conformation of [Leu5]-enkephalin specific for the delta receptors was analyzed and a comparison made with its crystal structure recently elucidated. |
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Keywords: | To whom correspondence should be addressed. |
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