2cf9

From Proteopedia

Revision as of 18:59, 3 May 2008

Template:STRUCTURE 2cf9

THROMBIN-METHOXY2

Overview

Two series of tricyclic inhibitors of the serine protease thrombin, imides (+/-)-1-(+/-)-8 and lactams (+/-)-9-(+/-)-13, were analysed to evaluate contributions of orthogonal multipolar interactions with the backbone C=O moiety of Asn98 to the free enthalpy of protein-ligand complexation. The lactam derivatives are much more potent and more selective inhibitors (K(i) values between 0.065 and 0.005 microM, selectivity for thrombin over trypsin between 361- and 1609-fold) than the imide compounds (Ki values between 0.057 and 23.7 microM, selectivity for thrombin over trypsin between 3- and 67-fold). The increase in potency and selectivity is explained by the favorable occupancy of the P-pocket of thrombin by the additional isopropyl substituent in the lactam derivatives. The nature of the substituent on the benzyl ring filling the D pocket strongly influences binding potency in the imide series, with Ki values increasing in the sequence: F < OCH2O < Cl < H < OMe < OH < N(pyr)<< Br. This sequence can be explained by both steric fit and the occurrence of orthogonal multipolar interactions with the backbone C[double bond, length as m-dash]O moiety of Asn98. In contrast, the substituent on the benzyl ring hardly affects the ligand potency in the lactam series. This discrepancy was clarified by the comparison of X-ray structures solved for co-crystals of thrombin with imide and lactam ligands. Whereas the benzyl substituents in the imide inhibitors are sufficiently close (< or =3.5 Angstroms) to the C=O group of Asn98 to allow for attractive orthogonal multipolar interactions, the distances in the lactam series are too large (> or =4 Angstroms) for attractive dipolar contacts to be effective.

About this Structure

2CF9 is a Protein complex structure of sequences from Homo sapiens. Full crystallographic information is available from OCA.

Reference

Multipolar interactions in the D pocket of thrombin: large differences between tricyclic imide and lactam inhibitors., Schweizer E, Hoffmann-Roder A, Olsen JA, Seiler P, Obst-Sander U, Wagner B, Kansy M, Banner DW, Diederich F, Org Biomol Chem. 2006 Jun 21;4(12):2364-75. Epub 2006 May 10. PMID:16763681 Page seeded by OCA on Sat May 3 21:59:38 2008