title: Conversion of type I 4:6 to 3:5 beta-turn types in human acidic fibroblast growth factor: effects upon structure, stability, folding, and mitogenic function.
abstract: Human acidic fibroblast growth factor (FGF-1) is a member of the beta-trefoil superfold, a protein architecture that exhibits a characteristic threefold axis of structural symmetry. FGF-1 contains 11 beta-turns, the majority being type I 3:5; however, a type I 4:6 turn is also found at three symmetry-related locations. The relative uniqueness of the type I 4:6 turn in the FGF-1 structure suggests it may play a key role in the stability, folding, or function of the protein. To test this hypothesis a series of deletion mutations were constructed, the aim of which was to convert existing type I 4:6 turns at two locations into type I 3:5 turns. The results show it is possible to successfully substitute the type I 4:6 turn by a type I 3:5 turn with minimal impact upon protein stability or folding. Thus, these different turn structures, even though they differ in length, exhibit similar energetic properties. Additional sequence swapping mutations within the introduced type I 3:5 turns suggests that the turn sequence primarily affects stability but not turn structure (which appears dictated primarily by the local environment). Although the results suggest that a stable, foldable beta-trefoil protein may be designed utilizing a single turn type (type I 3:5), a type I 4:6 turn at turn 1 of FGF-1 appears essential for efficient mitogenic function.
authors.affiliation: Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306-4300, USA.
authors.forename: Jihun
authors.initials: J
authors.lastname: Lee
authors.forename: Vikash Kumar
authors.initials: VK
authors.lastname: Dubey
authors.forename: Thayumanasamy
authors.initials: T
authors.lastname: Somasundaram
authors.forename: Michael
authors.initials: M
authors.lastname: Blaber
mesh_terms: D016475:3T3 Cells; D019943:Amino Acid Substitution; D000818:Animals; D002455:Cell Division / Q000187:drug effects; D018360:Crystallography, X-Ray; D004355:Drug Stability; D016220:Fibroblast Growth Factor 1 / Q000737:chemistry* / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D051379:Mice; D008958:Models, Molecular; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism
chemical_list: D011994:Recombinant Proteins; D016220:Fibroblast Growth Factor 1