Human fibrinogen: anticipating a 3-dimensional structure.

The principal component of blood clots is a protein meshwork called fibrin. The precursor protein, fibrinogen, occurs in a soluble form in the blood plasma where it is activated by thrombin when and if the need arises. More than a century after first being purified, fibrinogen has yet to have its detailed 3-dimensional structure revealed. The situation is changing rapidly, however, and crystallographic studies in progress in several laboratories on a variety of fragments and complexes may soon reveal not only its structure but also the subtleties of how this large glycoprotein is transformed into a fibrin clot.