Fibrinogen/fibrin domains

Figure 10.40. Formation of a Fibrin Clot. (1) Thrombin cleaves fibrinopeptides A and B from the central globule of fibrinogen. (2) Globular domains at the carboxyl-terminal ends of the P and y chains interact with "knobs" exposed at the amino-terminal ends of the P and a chains to form clots.

Comparative sequence analysis of even well described inter-protein interactions (i.e., from X-ray structure of multi-domain or subunit proteins) has only recently been possible initial results have however shown some common features of quaternary interactions. There is hope that interactions in naturally selfassociating proteins will be similar to those that lead to irreversible interactions in refolded proteins, and that one can then use this knowledge to prevent precipitation. For example, fibrin clots can be dissolved by adding the tetra-peptide Gly-Pro-Arg-Pro, the amino acids at the N-termini of fibrinogen molecules after thrombin cleavage. A related peptide, Arg-Gly-Asp-Ser, from the carboxy- terminus of fibrinogen, inhibits platelet aggregation. ... 

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