1ETS image
Entry Detail
PDB ID:
1ETS
Title:
REFINED 2.3 ANGSTROMS X-RAY CRYSTAL STRUCTURE OF BOVINE THROMBIN COMPLEXES FORMED WITH THE BENZAMIDINE AND ARGININE-BASED THROMBIN INHIBITORS NAPAP, 4-TAPAP AND MQPA: A STARTING POINT FOR IMPROVING ANTITHROMBOTICS
Biological Source:
Source Organism:
PDB Version:
Deposition Date:
1992-07-06
Release Date:
1994-01-31
Method Details:
Experimental Method:
Resolution:
2.30 Å
R-Value Work:
0.17
R-Value Observed:
0.17
Space Group:
P 42 21 2
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:EPSILON-THROMBIN
Chain IDs:B (auth: H)
Chain Length:259
Number of Molecules:1
Biological Source:Bos taurus
Polymer Type:polypeptide(L)
Description:EPSILON-THROMBIN
Chain IDs:A (auth: L)
Chain Length:49
Number of Molecules:1
Biological Source:Bos taurus
Ligand Molecules
Peptide-like Molecules
PRD_000451
Primary Citation
Refined 2.3 A X-ray crystal structure of bovine thrombin complexes formed with the benzamidine and arginine-based thrombin inhibitors NAPAP, 4-TAPAP and MQPA. A starting point for improving antithrombotics.
J.Mol.Biol. 226 1085 1099 (1992)
PMID: 1518046 DOI: 10.1016/0022-2836(92)91054-S

Abstact

Well-diffracting crystals of bovine epsilon-thrombin in complex with several "non-peptidic" benzamidine and arginine-based thrombin inhibitors have been obtained by co-crystallization. The 2.3 A crystal structures of three complexes formed either with NAPAP, 4-TAPAP, or MQPA, were solved by Patterson search methods and refined to crystallographic R-values of 0.167 to 0.178. The active-site environment of thrombin is only slightly affected by binding of the different inhibitors; in particular, the exposed "60-insertion loop" essentially maintains its typical projecting structure. The D-stereoisomer of NAPAP and the L-stereoisomer of MQPA bind to thrombin with very similar conformations, as previously inferred from their binding to bovine trypsin; the arginine side-chain of the latter inserts into the specificity pocket in a "non-canonical" manner. The L-stereoisomer of 4-TAPAP, whose binding geometry towards trypsin was only poorly defined, is bound to the thrombin active-site in a compact conformation. In contrast to NAPAP, the distal p-amidino/guanidino groups of 4-TAPAP and MQPA do not interact with the carboxylate group of Asp189 in the thrombin specificity pocket in a "symmetrical" twin N-twin O manner, but through "lateral" single N-twin O contacts; in contrast to the p-amidino group of 4-TAPAP, however, the guanidyl group of MQPA packs favourably in the pocket due to an elaborate hydrogen bond network, which includes two entrapped water molecules. These thrombin structures confirm previous conclusions of the important role of the intermolecular hydrogen bonds formed with Gly216, and of the good sterical fit of the terminal bulky hydrophobic inhibitor groups with the hydrophobic aryl binding site and the S2-cavity, respectively, for tight thrombin active site binding of these non-peptidic inhibitors. These accurate crystal structures are presumed to be excellent starting points for the design and the elaboration of improved antithrombotics.

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