FIG 11.

The recombinant human fibronectin fragment retronectin mediates gp120-α₄β₇ binding. (A) Plasma fibronectin, cellular fibronectin, and retronectin were biotinylated and tested for binding to RPMI8866 cells. The results of a single representative experiment are shown. (B) Western blot analysis of plasma fibronectin (pFn), cellular fibronectin (cFn), and retronectin. Shown are two parallel blots developed with either polyclonal fibronectin antiserum or monoclonal antibody to the fibronectin CS1 peptide; 1 μg of protein was loaded per lane. (C) Retronectin mediates gp120 binding to RPMI8866 cells. Biotinylated retronectin (+biotin) produces a binding signal, and nonbiotinylated retronectin (−biotin) does not. Binding of wild-type MW959 and MW959 with the V2 loop deleted was measured with (hatched bars) and without (solid bars) 2-h preincubation with retronectin. The results are the means and standard deviations of 3 replicate measures.