Thyroglobulin type 1 repeats are thought to be involved in the control of proteolytic degradation [2]. The domain usually contains six conserved cysteines. These form three disulphide bridges. Cysteines 1 pairs with 2, 3 with 4 and 5 with 6.

1: Crystal structure of MHC class II-associated p41 Ii fragment bound to cathepsin L reveals the structural basis for differentiation between cathepsins L and S. Guncar G, Pungercic G, Klemencic I, Turk V, Turk D; EMBO J 1999;18:793-803. PMID:10022822

2: Characterization of the type-1 repeat from thyroglobulin, a cysteine- rich module found in proteins from different families. Molina F, Bouanani M, Pau B, Granier C; Eur J Biochem 1996;240:125-133. PMID:8797845