Identification of an essential histidine residue for fibrin polymerization. Essential role of histidine 16 of the B beta-chain.

An essential histidine residue for fibrin polymerization has been identified. It is the one located at position 16 in the B beta-chain of fibrinogen by the following experiments. Photooxidation of the activated NH2-terminal disulfide knot, which is derived from fibrin and contains the NH2-terminal binding domain, reduced the ability of this fragment to bind to fibrinogen-Sepharose conjugate. Functional and dysfunctional fragments were separated by the affinity chromatography just mentioned. Sequence analyses have revealed that the histidine residue which should be obtained in the second stage of the cleavage is missing in the dysfunctional fragment. The histidine residue which is supposed to be found at the eighth step, however, was not modified under our experimental conditions.