The thrombospondin repeat is a short aspartate rich repeat which binds to calcium ions. The repeat was initially identified in thrombospondin proteins that contained 7 of these repeats [1]. The repeat lacks defined secondary structure [2].

1: The structure of human thrombospondin, an adhesive glycoprotein with multiple calcium-binding sites and homologies with several different proteins. Lawler J, Hynes RO; J Cell Biol 1986;103:1635-1648. PMID:2430973

2: Structure of a thrombospondin C-terminal fragment reveals a novel calcium core in the type 3 repeats. Kvansakul M, Adams JC, Hohenester E; EMBO J. 2004;23:1223-1233. PMID:15014436