Self-assembly and supramolecular organization of EMILIN

The primary structure of human Elastin microfibril interface-located protei n (EMILIN), an elastic fiber-associated glycoprotein, consists of a globula r Clq domain (gC1q) at the C terminus, a short collagenous stalk, a long re gion with a high potential for forming coiled-coil CY helices, and a cystei ne-rich N-terminal sequence. It is not known whether the EMILIN gC1q domain is involved in the assembly process and in the supramolecular organization as shown for the similar domain of collagen X By employing the yeast two-h ybrid system the EMILIN gC1q domains interacted with themselves, proving fo r the first time that this interaction occurs in vivo. The gC1q domain form ed oligomers running as trimers in native gels that were less stable than t he comparable trimers of the collagen X gC1q domain since they did not with stand heating. The collagenous domain was trypsin-resistant and migrated at a size corresponding to a triple helix under native conditions. In reducin g agarose gels, EMILIN also migrated as a trimer, whereas under non-reducin g conditions it formed polymers of many millions of daltons, A truncated fr agment lacking gC1q and collagenous domains assembled to a much lesser exte nt, thus deducing that the C-terminal domain(s) are essential for the forma tion of trimers that finally assemble into large EMILIN multimers.