Interdomain mobility and conformational stability of type III fibronectin domain pairs control surface adsorption, desorption and unfolding

Pereira, P. and Kelly, S.M. and Gellert, P.R. and van der Walle, Christopher F. (2008) Interdomain mobility and conformational stability of type III fibronectin domain pairs control surface adsorption, desorption and unfolding. Colloids and Surfaces B: Biointerfaces, 64 (1). pp. 1-9. ISSN 0927-7765 (http://dx.doi.org/10.1016/j.colsurfb.2007.12.015)

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Abstract

The 9th-10th type III fibronectin domain pair (9-10FNIII) has found widespread use as a biomimetic surface for cell adhesion. However, the effect of mutations to 9-10FNIII on its surface adsorption characteristics have not been investigated. Here we address this issue using total internal reflection fluorescence (TIRF) and circular dichroism spectroscopy, comparing two conformationally stable 9-10FNIII mutants against the wild type. Desorption of the 9-10FNIII mutants from the silica surface was minimal in comparison to desorption of 9-10FNIII. The extent and rate of protein desorption from silica was empirically matched by loss of secondary structure upon adsorption, with only the spectrum for 9-10FNIII showing extensive loss of the β-sandwich fold. For the proteins adsorbed to hydrophobic surfaces, only the CD spectra for the 9-10FNIII mutant constrained via an interdomain disulphide bridge showed similarity with the corresponding solution structure. Since the binding of 9-10FNIII to integrin α5β1 is highly dependent on the relative spatial arrangement of the two domains, we suggest that the observed differences in cell adhesion and spreading on wild type 9-10FNIII and mutants may in part be attributed to the extent of protein desorption and unfolding at the surface.

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