Thrombin inhibition by cyclic peptides from thrombomodulin. |
| |
| Authors: | J. C. Lougheed C. L. Bowman D. P. Meininger E. A. Komives |
| |
| Affiliation: | Department of Chemistry and Biochemistry, University of California-San Diego, La Jolla 92093-0601, USA. |
| |
| Abstract: | Peptides corresponding to the loop regions of the fourth, fifth, and sixth epidermal growth factor (EGF)-like domains of thrombomodulin (TM) have been synthesized and assayed for thrombin inhibition, as indicated by both inhibition of thrombin-mediated fibrinogen clotting and inhibition of the association of thrombin with TM that results in protein C activation. Peptides from the fifth EGF-like domain showed significant inhibition of fibrinogen clotting and protein C activation, whereas peptides from the fourth and sixth EGF-like domains were weak inhibitors in both assays. Two structural features were important for inhibitory potency of the peptides from the fifth EGF-like domain: cyclization by a disulfide bond and attachment of the "tail" amino acids C-terminal to the disulfide loop. Linear control peptides did not significantly inhibit clotting or protein C activation. The C-terminal loop alone, the "tail" peptide, or a mixture of the two were at least 10-fold less potent inhibitors of clotting or protein C activation. A more constrained peptide analog was designed by deletion of an isoleucine within the C5-C6 disulfide loop, TM52-1 + 5C. This analog was a better inhibitor in both assay systems, having a Ki for protein C activation of 26 microM. |
| |
| Keywords: | disulfide bonds EGF-like domains protein C protein-protein interactions |
|
|
