During the last few years much of the controversy about the general structure of fibrinogen has been resolved. Electron microscope (EM) studies by many groups have confirmed the pioneer observations by Hall & Slayter (1) of an extended multidomained molecule. The completion of the amino acid sequence of human fibrinogen (2-6) and the assignment of disulfide bonds (7-9) have provided data that are in complete harmony with such a structure, especially when regarded in the light of a host of proteolytic and chemical fragmentation studies. With regard to the latter, two sets of fibrinogen fragments have proved enormously important in the unraveling of the structure. These are the fragments generated by plasmin (10), on the one hand, and cyanogen bromide treatment (1 1), on the other. The plasmin products include families of core fragments designated D and E as well as the transient intermediates denoted X and Y. The most important cyanogen bromide fragment is a large-molecular-weight entity referred to as the amino-terminal disulfide knot (N-DSK)(11) that enjoys an 80% reciprocal overlap with fragment E (12). The field still suffers from the lack of a genuine crystal structure for either the major fragments or the native protein.

During the past few years several reviews on the fibrinogen-fibrin system have appeared (13, 14). In addition, there have been some large meetings devoted to the subject, the proceedings of which have been published (l5-17). This review concentrates on articles published in the last five years.