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A Light Scattering Study of the Interaction of Fibroblast Growth Factor (FGF) with its Receptor

Pallavi Sharma ^*, Dakshinamurthy Rajalingam , Thallapuranam Krishnaswamy Suresh Kumar  and Surendra Singh ^*

^* Physics Department, and Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas

Correspondence: Address reprint requests and inquiries to T. K. S. Kumar, E-mail: sthalla{at}uark.edu; or to S. Singh, E-mail: ssingh{at}uark.edu.

Light scattering technique has been used to study the interaction between fibroblast growth factor (FGF) and its receptor. In this study, a general mathematical model has been developed where the concentration of product formed by the interaction of two proteins and its dependence on the initial concentration of interacting proteins have been determined using laser light scattering. Calculated hydrodynamic diameters reveal that both human fibroblast growth factor (hFGF-1) and its receptor domain (D2 domain) exist as monomers in solution. Titration of hFGF-1 and the D2 domain of FGFR show that they interact in a 1:1 stoichiometry in solution. The binding stoichiometry does not depend on the concentrations of the interacting proteins. The results of this study, for the first time to our knowledge, provide an unambiguous evidence that the 2:2 binary complex of FGF and FGFR observed in the crystal structures of the FGF-FGFR complex (in the absence of heparin) is possibly a crystallization artifact.