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J Mol Biol 371(1), 256-268 2007[DOI Link]
Spackling the crack: stabilizing human fibroblast growth factor-1 by targeting the N-and C-terminus β-strand interactionsDubey VK, Lee J, Somasundaram T, Blaber S, and Blaber M.
Departments of Chemistry and Biochemistry and Biomedical Science and the Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida 32306-4380, USA.
The β-trefoil protein human fibroblast growth factor-1 (FGF-1) is made up of a
six-stranded anti-parallel β-barrel closed off on one end by three β-hairpins, thus exhibiting a
three-fold axis of structural symmetry. The N- and C-terminus β-strands hydrogen bond to each
other and their interaction is postulated from both NMR and x-ray structure data to be important
in folding and stability. Specific mutations within the adjacent N- and C-terminus â-strands of
FGF-1 are shown to provide a substantial increase in stability. This increase is largely correlated
with an increased folding rate constant, and with a smaller but significant decrease in the
unfolding rate constant. A series of stabilizing mutations are subsequently combined and result
in a doubling of the ΔG of unfolding. When taken in the context of previous studies of stabilizing
mutations, the results indicate that although FGF-1 is known for generally poor thermal stability,
the β-trefoil architecture appears capable of substantial thermal stability. Targeting stabilizing
mutations within the N- and C-terminus β-strand interactions of a β-barrel architecture may be a
generally useful approach to increase protein stability. Such stabilized mutations of FGF-1 are
shown to exhibit significant increases in effective mitogenic potency, and may prove useful as
"second generation" forms of FGF-1 for application in angiogenic therapy.