Do the isolated fibrinogen alphaC-domains form ordered oligomers?

Previous electron microscopy (EM) studies revealed that the proteolytically prepared, truncated, bovine fibrinogen alphaC-domain (Aalpha223-539 fragment) upon transfer from acidic to neutral pH formed ordered oligomers which could mimic alpha polymers of cross-linked fibrin. In this study, we demonstrated that although its recombinant analog, bAalpha224-538, as well as the full-length version of the alphaC-domain (bAalpha224-568), upon similar treatment also formed oligomers with ordered structure, both were monomeric when kept in neutral pH buffer. To search further for conditions for their oligomerization, we treated bAalpha224-568 with factor XIIIa, purified the cross-linked soluble fraction, and confirmed that it consisted of oligomers. Similar cross-linked oligomers were obtained with the recombinant human alphaC-domain (residues Aalpha221-610). In a cell adhesion assay, the adhesion of human umbilical vein endothelial cells (HUVEC) to the alphaC-domains substantially increased upon oligomerization. These results demonstrate that the recombinant alphaC-domains can form stable oligomers which may mimic properties of the alphaC-domains in cross-linked fibrin.