Key regulator of transforming growth factor beta (TGFB1, TGFB2 and TGFB3) that controls TGF-beta activation by maintaining it in a latent state during storage in extracellular space. Associates specifically via disulfide bonds with the Latency-associated peptide (LAP), which is the regulatory chain of TGF-beta, and regulates integrin-dependent activation of TGF-beta (By similarity). Able to outcompete LTBP1 for binding to LAP regulatory chain of TGF-beta (By similarity). Controls activation of TGF-beta-1 (TGFB1) on the surface of activated regulatory T-cells (Tregs). Required for epithelial fusion during palate development by regulating activation of TGF-beta-3 (TGFB3) (By similarity). Interacts with TGFB1; associates via disulfide bonds with the Latency-associated peptide chain (LAP) regulatory chain of TGFB1, leading to regulate activation of TGF-beta-1. Interacts with TGFB2 (By similarity). Interacts with TGFB3; associates via disulfide bonds with the Latency-associated peptide chain (LAP) regulatory chain of TGFB3, leading to regulate activation of TGF-beta-3 (By similarity). Interacts with LAPTM4B; decreases TGFB1 production in regulatory T-cells (By similarity). Belongs to the LRRC32/LRRC33 family.