Figure 5.

Binding between the 8-Cys repeat of LTBP-1 and Cys-33 of TGF-β1•LAP is mediated by a direct disulfide exchange. Constructs pJS-4 or pJS-24 were transfected with wild-type pTGFβ1 or pTGFβ1 C223,225S to COS-7 cells. The secreted proteins were separated by 7.5% PAGE and detected by immunoblotting with β1•LAP antibodies (top panel). Brackets on the right indicate the free or complexed β1•LAP forms. The expression of proteins coded by LTBP-constructs was verified by 4–15% gradient PAGE followed by anti-HA immunoblot (middle panel). Secretion of TGF-β1 was detected by immunoblotting for TGF-β1 (bottom panel, an arrow). Below the immunoblots is a model illustrating the proposed β1•LAP - 8-Cys repeat interaction.