Fig. 6.

Characterization of heterologously expressed soluble F11. Soluble F11 that was isolated from culture supernatants of transfected COS cells by immunoaffinity chromatography was characterized by SDS-PAGE followed by silver staining (a–c) or Western blot analysis with an F11-specific monoclonal antibody (d–f). F11 isolated from chick brain (a, 600 ng; d, 120 ng) is compared with recombinant soluble F11 (b, 1.6 μg;e, 320 ng). The latter contains a 53 kDa contaminant (b), which is unrelated to F11 (e) and which is also found in preparations of other recombinant proteins isolated from tissue culture supernatants, for instance, the 23 kDa DiFc protein (c, 3.2 μg;f, 640 ng), which consists of two IgG Fc domains (our unpublished data). Because preparations of the DiFc protein did not enhance neurite outgrowth of retinal neurons on FN (data not shown), suggesting that the 53 kDa protein does not interfere with aspects of this study, we did not attempt to separate the contaminant from recombinant F11.