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Title: Structural studies of fibroblast growth factors and their receptors
Author: Harmer, N. J.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2004
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Recent crystal structures have suggested two models for the complex between FGFs, FGF receptors (FGFRs) and the proteoglycan heparin that mediates signalling, and have provided insight into how FGFs show differing affinities for the range of FGFRs. I have examined complexes of FGF, FGFR and heparin by size-exclusion chromatography, analytical ultracentrifugation and mass spectrometry. This analysis suggests that both of the crystal structures faithfully represent the state of the molecules in solution. From this, I conclude that the origin of the difference in the two models lies in the preparation of the complexes, and propose a resolution of the controversy. Using longer heparan sulphate fragments, I have observed larger complexes with FGF and FGFR. Further study of these complexes provides compelling evidence that these larger complexes correspond to a dimer of the FGF-FGFR complexes previously observed. These larger complexes give an insight into how higher order complexes of FGFs and FGFRs may form on the cell surface. FGF19, one of the most divergent human FGFs, is unique in binding solely to one receptor, FGFR4. Having cloned the human FGF19 gene, I devised a strategy of expression and purification to provide sufficient quantities of pure FGF19 for crystallisation. I have used molecular replacement to solve the crystal structure of FGF19 at 1.3 A resolution. The structure shows that two novel disulphide bonds found in FGF19, one of which appears to be conserved among several of the other FGFs, stabilise extended loops. The key heparin binding loops of FGF19 have radically different conformations and charge patterns, compared to other FGFs, correlating with the unusually low affinity of FGF19 for heparin. A model for the complex of FGF19 with FGFR4 demonstrates that sequences unique to both FGF19 and FGFR4 are key to the formation of the complex. The structure therefore offers a clear explanation for the unusual affinity of FGF19 for FGFR4 alone.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available