Proton and tritium nmr relaxation studies of peptide inhibitor binding to bacterial collagenase: Conformation and dynamics

✍ Scribed by Vincent Dive; Adolfo Lai; Gianni Valensin; Giuseppe Saba; Athanasios Yiotakis; Flavio Toma

• Publisher: Wiley (John Wiley & Sons)
• Year: 1991
• Tongue: English
• Weight: 1004 KB
• Volume: 31
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360310305

✦ Synopsis

Abstract

The interaction of succinyl‐Pro‐Ala, a competitive inhibitor of Achromobacter iophagus collagenase, with the enzyme was studied by longitudinal proton and tritium relaxation. Specific deuterium and tritium labeling of the succinyl part at vicinal positions allowed the measurement of the cross‐relaxation rates of individual proton or tritium spin pairs in the inhibitor–enzyme complex as well as in the free inhibitor. Overall correlation times, internuclear distances, and qualitative information on the internal mobility in Suc^1^ (as provided by the generalized order parameter S^2^) could be deduced by the comparison of proton and tritium cross‐relaxations of spin pairs at complementary positions in the CH~2~CH~2~ moiety as analyzed in terms of the model‐free approach by Lipari and Szabo.

The conformational and motional parameters of the inhibitor in the free and enzyme‐bound state were directly compared by this method. The measurement of proton cross‐relaxation in the Ala residue provided additional information on the inhibitor binding. The determination of the order parameter in different parts of the inhibitor molecule in the bound state indicates that the succinyl and alanyl residues are primarily involved in the interaction with the enzyme active site. The succinyl moiety, characterized in solution by the conformational equilibrium among the three staggered rotamers–i.e., trans: 50%; g^+^: 20%; g^−^; 30%–adopted in the bound state the unique trans conformation.