The present invention relates to a TGF-.beta.1 binding protein called r150. This protein has a GPI-anchor contained in r150 itself and not on a tightly associated protein and that it binds TGF-.beta.1 with an affinity comparable to those of the signaling receptors. Furthermore, the released (soluble) form of this protein binds TGF-.beta.1 independent of the types I and II receptors. Also, the soluble form inhibits the binding of TGF-.beta. to its receptor. In addition, evidence that r150 is released from the cell surface by an endogenous phospholipase C is provided. Also, the creation of a mutant human keratinocyte cell line with a defect in GPI synthesis which displays reduced expression of r150 is described. Our results using these mutant keratinocytes suggest that the membrane anchored form of r150 is a negative modulator of TGF-beta responses. These findings, taken together with the observation that r150 forms a heteromeric complex with the signaling receptors, suggest that this accessory receptor in either its membrane anchored or soluble form may antagonize TGF-.beta. responses in human keratinocytes. Experiments with mutants confirmed that TGF.beta.1 activity can be modulated when the expression of the accessory receptor r150 is silenced. The complete nucleic acid and deduced amino acid sequences are now provided. The r150 cloned nucleic acid was used to study overexpression of r150. When r150 gene is overexpressed, TGF.beta. responses are increased. r150 and its derivatives or precursors (fragments, variants and nucleic acids encoding the same) will find a broad clinical utility, knowing that TGF.beta.1 is an important cytokine.