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Rational Design of Protein Stability: Effect of (2S,4R)-4-Fluoroproline on the Stability and Folding Pathway of Ubiquitin

PLoS One, May 2011, Vol.6(5), p.e19425 [Peer Reviewed Journal]

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  • Title:
    Rational Design of Protein Stability: Effect of (2S,4R)-4-Fluoroproline on the Stability and Folding Pathway of Ubiquitin
  • Author: Crespo, Maria ; Rubini, Marina
  • Found In: PLoS One, May 2011, Vol.6(5), p.e19425 [Peer Reviewed Journal]
  • Subjects: Protein Folding ; Fluorine ; Biochemistry ; Biosynthesis ; Biological Effects ; Biological Activity ; Amino Acids ; Biology ; Protein Folding ; Ubiquitin ; Peptides ; Biological Activity ; Denaturation ; Chirality ; Chirality ; Proteins ; Proline ; Pyrrolidine ; Studies ; Denaturation ; Peptides ; Stability Analysis ; Protein Structure ; Peptides ; Proteins ; Proline ; Fluorination ; Derivatives ; Structural Stability ; E Coli ; E Coli ; Proline ; Protein Structure ; Fluorescence ; Fluorine ; Fluorescence Spectrometry ; Globular Proteins ; Protein Folding ; Thermal Stability
  • Language: English
  • Description: Background Many strategies have been employed to increase the conformational stability of proteins. The use of 4-substituted proline analogs capable to induce pre-organization in target proteins is an attractive tool to deliver an additional conformational stability without perturbing the overall protein structure. Both, peptides and proteins containing 4-fluorinated proline derivatives can be stabilized by forcing the pyrrolidine ring in its favored puckering conformation. The fluorinated pyrrolidine rings of proline can preferably stabilize either a Cγ-exo or a Cγ-endo ring pucker in dependence of proline chirality (4R/4S) in a complex protein structure. To examine whether this rational strategy can be generally used for protein stabilization, we have chosen human ubiquitin as a model protein which contains three proline residues displaying Cγ-exo puckering. Methodology/Principal Findings While (2S,4R)-4-fluoroproline ((4R)-FPro) containing ubiquitinin can be expressed in related auxotrophic Escherichia coli strain, all attempts to incorporate (2S,4S)-4-fluoroproline ((4S)-FPro) failed. Our results indicate that (4R)-FPro is favoring the Cγ-exo conformation present in the wild type structure and stabilizes the protein structure due to a pre-organization effect. This was confirmed by thermal and guanidinium chloride-induced denaturation profile analyses, where we observed an increase in stability of −4.71 kJ·mol−1 in the case of (4R)-FPro containing ubiquitin ((4R)-FPro-ub) compared to wild type ubiquitin (wt-ub). Expectedly, activity assays revealed that (4R)-FPro-ub retained the full biological activity compared to wt-ub. Conclusions/Significance The results fully confirm the general applicability of incorporating fluoroproline derivatives for improving protein stability. In general, a rational design strategy that enforces the natural occurring proline puckering conformation can be used to stabilize the desired target protein.
  • Identifier: E-ISSN: 19326203 ; DOI: 10.1371/journal.pone.0019425

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