Solution structure of the N-terminal F1 module pair from human fibronectin

Multiple sites within the N-terminal domain (^1-5F1) of fibronectin have been implicated previously in fibronectin matrix assembly, heparin binding, and binding to cell surface proteins of pathogenic bacteria. The solution structure of ¹F1²F1, the N-terminal F1 module pair from human fibronectin, has been determined using NMR spectroscopy. Both modules in the pair conform to the F1 consensus fold. In ⁴F1⁵F1, the only other F1 module pair structure available, there is a well-defined intermodule interface; in ¹F1²F1, however, there is no detectable interface between the modules. Comparison of the backbone ¹⁵N-{¹H} NOE values for both module pairs confirms that the longer intermodule sequence in ¹F1²F1 is flexible and that the stabilization of the ⁴F1 C-D loop observed in ⁴F1⁵F1, as a result of the intermodule interface, is not observed in ¹F1²F1.