Fibrinopeptides amino acid sequence

Scheme 21 Amino Acid Sequence of a Segment of Fibrinopeptide A and Its p-Turn Peptidomimeticsl%l...

Figure 2.4 Tandem mass spectrum obtained for fibrinopeptide A. A solution of fibrinopeptide A at 33fmol j.L 1 was infused at a flow rate of 200-300nLmin 1 from reservoir 1 using the conditions indicated in Figure 2.3A. The buffer was 10mM acetic acid, pH = 3.0, containing 10% (v/v) methanol. The Y ion series is indicated by full lines. The B ion series is indicated by broken lines. The letters in the right upper corner indicate the fibrinopeptide A amino acid sequence in the one-letter code. (Adapted with permission from Ref. 7).

FIGURE 3.28 Simplified spectrum of y ions showing the amino acid sequence of glutamine fibrinopeptide B. 

Fibrin polymerization is initiated by the enzymatic cleavage of the fibrinopeptides, converting fibrinogen to fibrin monomer (Fig. 1). Then, several nonenzymatic reactions yield an orderly sequence of macromolec-ular assembly steps. Several other plasma proteins bind specifically to the resulting fibrin network. The clot is stabilized by covalent ligation or crosslinking of specific amino acids by a transglutaminase, Factor XHIa. 

Top) peptide ladder sequencing principle. Phenyl isothiocyanate (PITC) produces phenylthiohydantoin (PTH) of the terminal amino acid and a new peptide with one less amino acid. Phenyl isocyanate (PIC), in low quantity, produces N-terminal phenylcarba-mate (PC) from a small fraction of each peptide. (Bottom) example of sequencing of [Glu1]fibrinopeptide B. Reproduced (modified) from Chait B.T., Wang R., Beavis R.C. and Kent S.B.H., Science, 262, 89, 1993, with permission. 

Fibrinopeptides the two pairs of peptides (A and B) cleaved from the /V-termini of the 2a and 2P chains of fibrinogen by thrombin. F. arise by cleavage of Arg-GIy bon so that Arg is the C-terminal end of the F, and Gly is the A/-terminal end of the a and P chains of fibrin. Human FA. is Ala-Asp-Ser-Gly-Glu-Gly-Asp-Phe-Leu-Ala-Glu-(Gly)3-Val-Arg, and human F.B. is Pyr-Glu-Gly-Val-Asn-Asp-Asn-(Glu)2-Gly-(Phe)2-Ser-Ala-Arg. F.A. ranges in size from 14 amino acids (horse, lizard) to 19 (cattle), and F.B. from 9 (rhesus monkeys) to 21 (cattle, elk and kangaroo). The sequences of the F. have been used to establish a detailed phylogenetic tree for mammals which is very similar to the classical one. The F. have a vasoconstrictive effect which serves to keep the coagulation principles from being removed too quickly from an injury site. 

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