Distinctive role of histidine-16 of the B beta chain of fibrinogen in the end-to-end association of fibrin.

Photooxidation of fibrinogen reduced the batroxobin-induced fibrin polymerization. The fibrin fragment des-AB N-DSK, which contains the binding sites termed A and B, lost the ability to bind to the site termed a in fibrinogen-Sepharose upon the oxidation of histidine-16 in the B beta chain of fibrinogen [Shimizu, A., Saito, Y., Matsushima, A. & Inada, Y. (1983) J. Biol. Chem. 258, 7915-7917]. Some of the fragments, which became unable to bind to fibrinogen-Sepharose due to the destruction of site A, however, retained the ability to bind to D-dimer-Sepharose, which contains both sites a and b. This shows that histidine-16 of the B beta chain of fibrinogen is essential for site A but may not be essential for site B. It is of interest that histidine-16 of the B beta chain, which is only one residue away from the thrombin-susceptible bond, makes a part of the site A for the end-to-end association created by the release of fibrinopeptide A.