FIGURE 7.

Diagram of how FUD and HADD may cause expansion of plasma FN. Plasma FN in a conceptual compact conformation (top) or extended conformation (bottom). One subunit is drawn with completely filled symbols, the other with outlined symbols. The complete dimer is shown in the compact conformation, and one subunit and part of the second is shown for the extended conformation. Only selected modules are numbered. The subunits are held together by disulfides at the C termini and interactions of ^12–14FNIII with ^2–3FNIII (red three-dimensional box). Each subunit is further constrained by the ⁴FNI-³FNIII interaction (pink diamond). FUD or HADD, which by themselves are random coils, form β-zippers with the indicated FNI modules, resulting in unfolding and expansion of the quaternary structure. The epitope for mAbIII-10 used to monitor conformational change is in ¹⁰FNIII (red dot).