Background: Fibroblast growth Factor Homologous Factors (FHFs) belong to a subclass
of Fibroblast Growth Factor (FGF) family owing to their high sequence and structural similarities
with FGFs. However, despite these similarities, there are properties which set them apart from
FGFs. FHFs lack the secretion signal sequence unlike other FGF members, except FGF1 and 2.
Unlike FGFs, FHFs are not able to bind to FGF Receptors (FGFRs) and instead have been
implicated in binding to Voltage-Gated Sodium Channels (VGSCs), neuronal MAP kinase scaffold
protein and islet-brain-2 (IB2). The two amino acids Arg-52 and Val95 are conserved in all FHFs
and mutation of these residues lead to its inability to bind with VGSC/IB2. However, it is not clear
whether the loss of binding is due to destabilization of the protein on mutation or due to
involvement of Arg52 and Val95 in conferring functionality to FHFs.
Objective: In the present study, we have mutated these two conserved residues of FHF2 with its
corresponding FGF counterpart amino acids and studied the effects of the mutations on the
structure and stability of the protein.
Methods: Several biophysical methods like isothermal equilibrium denaturation study, ANS
fluorescence, intrinsic fluorescence, acrylamide quenching, circular dichroism studies as well as
using computational approaches were employed.
Results: The single mutations were found to affect the overall stability, conformation and
functionality of the protein.
Conclusion: Thus, the studies throw light on the role of specific amino acids in deciding the
stability, structure and functionality of proteins and will be useful for development of
therapeutically engineered proteins.