Calcium-binding Thrombospondin type 3 (TSP3) repeat; C-type motif 1C
TSP3 repeats of the vertebrate thrombospondin (TSP)-1,-2,-3,-4 and TSP-5/also known as COMP (cartilage oligomeric matrix protein), and related proteins. These short aspartate-rich repeats are a continuous series of calcium binding sites that can be divided into two sequence motifs: N-type and C-type. N-type and C-type motifs are distinguished by their sequence length, calcium ion binding, and their interactions with water molecules. C-type motifs are higher affinity binding sites compared to N-type motifs. The first TSP3 repeat 1C deviates from the canonical C-type calcium binding repeat in containing an insert relative to the other C-type repeats, however, the residues of the interrupted halves are positioned identically to C-type repeats without the insert.