Fig. 4. Domain structures of fibrillin-1 and elastin, showing molecular interaction sites identified in vitro (see Molecular Interactions). (A) Fibrillin-1 has 47 cbEGF-like domains, interspersed with TB modules. A proline-rich region is towards the N-terminus. N-glycosylation sites are indicated. (B) Elastin contains alternating hydrophobic and crosslinking domains. The C-terminus has two cysteines and a negatively charged pocket.