1b2h
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Oligo-Peptide Binding Protein Complexed with Lysyl-Ornithyl-Lysine
OverviewOverview
The oligopeptide-binding protein OppA provides a useful model system for, studying the physical chemistry underlying noncovalent interactions since, it binds a variety of readily synthesized ligands. We have studied the, binding of eight closely related tripeptides of the type Lysine-X-Lysine, where X is an abnormal amino acid, by isothermal titration calorimetry, (ITC) and X-ray crystallography. The tripeptides fall into three series of, ligands, which have been designed to examine the effects of small changes, to the central side chain. Three ligands have a primary amine as the, second side chain, two have a straight alkane chain, and three have ring, systems. The results have revealed a definite preference for the binding, of hydrophobic residues over the positively charged side chains, the, latter binding only weakly due to unfavorable enthalpic effects. Within, the series of positively charged groups, a point of lowest affinity has, been identified and this is proposed to arise from unfavorable, electrostatic interactions in the pocket, including the disruption of a, key salt bridge. Marked entropy-enthalpy compensation is found across the, series, and some of the difficulties in designing tightly binding ligands, have been highlighted.
About this StructureAbout this Structure
1B2H is a Single protein structure of sequence from Salmonella typhimurium with ACT and U1 as ligands. Full crystallographic information is available from OCA.
ReferenceReference
Relating structure to thermodynamics: the crystal structures and binding affinity of eight OppA-peptide complexes., Davies TG, Hubbard RE, Tame JR, Protein Sci. 1999 Jul;8(7):1432-44. PMID:10422831
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