Inter-alpha-trypsin inhibitors (ITIs) consist of one light chain and a variable set of heavy chains. ITIs play a role in extracellular matrix (ECM) stabilisation and tumour metastasis as well as in plasma protease inhibition [1]. The vault protein inter-alpha-trypsin (VIT) domain described here is found to the N-terminus of a von Willebrand factor type A domain (Pfam:PF00092) in ITI heavy chains (ITIHs) and their precursors.

1: ITIH5, a novel member of the inter-alpha-trypsin inhibitor heavy chain family is downregulated in breast cancer. Himmelfarb M, Klopocki E, Grube S, Staub E, Klaman I, Hinzmann B, Kristiansen G, Rosenthal A, Durst M, Dahl E; Cancer Lett 2004;204:69-77. PMID:14744536

2: VIT-1: the second member of a new branch of the von Willebrand factor A domain superfamily. Mayne R, Ren ZX, Liu J, Cook T, Carson M, Narayana S; Biochem Soc Trans. 1999;27:832-835. PMID:10830112