Amide proton exchange rates of a bound pepsin inhibitor determined by isotope-edited proton NMR experiments.

Fesik SW, Luly JR, Stein HH, BaMaung N
Biochem Biophys Res Commun. 1987 147 (3): 892-8

PMID: 2822045 · DOI:10.1016/s0006-291x(87)80154-7

From a series of isotope-edited proton NMR spectra, amide proton exchange rates were measured at 20 degrees C, 30 degrees C, and 40 degrees C for a tightly bound 15N-labeled tripeptide inhibitor of porcine pepsin (IC50 = 1.7 X 10(-) M). Markedly different NH exchange rates were observed for the three amide protons of the bound inhibitor. The P1 NH exchanged much more slowly than the P2 NH and P3 NH. These results are discussed in terms of the relative solvent accessibility in the active site and the role of the NH protons of the inhibitor for hydrogen bonding to the enzyme. In this study a useful approach is demonstrated for obtaining NH exchange rates on ligands bound to biomacromolecules, the knowledge of which could be of potential utility in the design of therapeutically useful nonpeptide enzyme inhibitors from peptide leads.

MeSH Terms (10)

Amides Chemical Phenomena Chemistry, Physical Magnetic Resonance Spectroscopy Pepsin A Protease Inhibitors Protein Conformation Protons Structure-Activity Relationship Temperature

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