TINAG is a basement membrane glycoprotein initially identified as a target of antibodies in some forms of immunologically mediated tubulointerstitial nephritis.

TIN1 also contains a characteristic laminin-like epidermal growth factor (EGF) motif, 6 potential N-linked glycosylation sites, and a C-terminal region showing significant homology to the cathepsin family of cysteine proteinases . Northern blot analysis detected restricted expression of 2 TINAG transcripts in kidney and intestine: a 1.8-kb transcript corresponding to the TIN1 isoform and a 1.3-kb transcript thought to correspond to the TIN2 isoform.