Fibrillin-1 is an extracellular acidic protein with a high cysteine content and an extended thread-like shape with mosaic composition of different types of extracellular modules. Most of the fibrillin molecule is contributed by 47 epidermal growth factor-like (EGF-like) repeats; 43 of them have a consensus sequence for calcium binding (cb). Other modules including 8-cysteine motifs (seven), hybrid motifs (two), and unique domains (three) are interspersed throughout the molecule. Fibrillin-1 contains a proline-rich region close to the N-terminusthatisreplacedbyaglycine-richregioninfibrillin-2. The fibrillins are found throughout the connective tissue as integral components of extended fibrils.