Propensity for cis‐Proline Formation in Unfolded Proteins. (16th November 2017)

• Record Type: Journal Article
• Authors: Alderson, T. Reid; Lee, Jung Ho; Charlier, Cyril; Ying, Jinfa; Bax, Ad
• Is Part Of: Chembiochem. Volume 19:Number 1(2018)
• Page Start: 37
• Page End: 42
• Publication Date: 2017-11-16
• Subjects: alpha-synuclein -- cis-proline -- high pressure -- isomerization -- NMR spectroscopy -- protein folding; Biochemistry -- Periodicals; Molecular biology -- Periodicals; Pharmaceutical chemistry -- Periodicals; 572
• DOI: 10.1002/cbic.201700548
• Languages: English
• ISSNs: 1439-4227

Abstract

Abstract: In unfolded proteins, peptide bonds involving Pro residues exist in equilibrium between the minor cis and major trans conformations. Folded proteins predominantly contain trans ‐Pro bonds, and slow cis – trans Pro isomerization in the unfolded state is often found to be a rate‐limiting step in protein folding. Moreover, kinases and phosphatases that act upon Ser/Thr−Pro motifs exhibit preferential recognition of either the cis ‐ or trans ‐Pro conformer. Here, NMR spectra obtained at both atmospheric and high pressures indicate that the population of cis ‐Pro falls well below previous estimates, an effect attributed to the use of short peptides with charged termini in most prior model studies. For the intrinsically disordered protein α‐synuclein, cis ‐Pro populations at all of its five X−Pro bonds are less than 5 %, with only modest ionic strength dependence and no detectable effect of the previously demonstrated interaction between the N‐ and C‐terminal halves of the protein. Comparison to small peptides with the same amino‐acid sequence indicates that peptides, particularly those with unblocked, oppositely charged amino and carboxyl end groups, strongly overestimate the amount of cis ‐Pro. Abstract : Quid Pro quo : Multidimensional NMR spectroscopy was used to quantify cis ‐Pro peptide bond fractions in three unfolded proteins. The cis values are systematically lower than those in the corresponding short peptides; this is attributed to reduced conformational entropy in the antiparallel segments preceding and following the cis ‐Pro peptide bonds and to electrostatic attraction between oppositely charged termini in unblocked peptides.