Molecular properties of lamprey fibrinogen.

Application of conventional methods not previously used for preparing lamprey fibrinogen has yielded preparations of very high purity and stability. These preparations made possible a detailed evaluation of molecular weights in normal and chaotropic buffers. The native molecule repeatedly gave a molecular weight of 352,000 to 358,000 via sedimentation equilibrium in citrate buffer; a molecular weight of 354,500 was obtained in guanidine buffer. An anomalous increase of the value of the measured apparent partial specific volume was observed in guanidine buffer. Molecular weight data of the reduced and alkylated subunits of lamprey fibrinogen, obtained by four different methods, have led us to assign molecular weights of 110,000 for (A)alpha, 72,000 for (B) beta, and 50,000 for gamma. Based upon these molecular weights obtained for the subunits, as well as that of the native fibrinogen molecule, the subunit composition can best be fitted to the formulation [(A)n alpha, (B) beta 2, gamma 2] rather than the conventional[(A) alpha 2, (B) beta 2, gamma 2] which would yield a molecular weight of 464,000. Analysis of a stabilized clot induced by Ca2+ showed only gamma dimers; alpha subunit polymerization was undetectable. Cross-linking of lamprey fibrin in the presence of dansylcadaverine and Ca2+ results in fluorescent labeling of the gamma chains and to a lesser extent the gamma dimer. Differing from other reported vertebrate cross-linking systems, the lamprey fibrin alpha subunit appears essentially unreactive in both polymer formation and dansylcadaverine incorporation. These distinct molecular properties may be reasonably attributed to the existence of the single (A)n alpha subunit in the molecular structure of the molecule.