Kinetics of contact formation and end-to-end distance distributions of swollen disordered peptides
Articolo
Data di Pubblicazione:
2009
Citazione:
Kinetics of contact formation and end-to-end distance distributions of swollen disordered peptides / A. Soranno, R. Longhi, T. Bellini, M. Buscaglia. - In: BIOPHYSICAL JOURNAL. - ISSN 0006-3495. - 96:4(2009 Feb 18), pp. 1515-1528.
Abstract:
Unstructured polypeptide chains are subject to various degrees of swelling or compaction depending on the
combination of solvent condition and amino acid sequence. Highly denatured proteins generally behave like random-coils
with excluded volume repulsion, whereas in aqueous buffer more compact conformations have been observed for the lowpopulated
unfolded state of globular proteins as well as for naturally disordered sequences. To quantitatively account for the
different mechanisms inducing the swelling of polypeptides, we have examined three 14-residues peptides in aqueous buffer
and in denaturant solutions, including the well characterized AGQ repeat as a reference and two variants, in which we have
successively introduced charged side chains and removed the glycines. Quenching of the triplet state of tryptophan by close
½AQ1 contact with cysteine has been used in conjunction with Fo¨ rster resonance energy transfer to study the equilibrium and kinetic
properties of the peptide chains. The experiments enable accessing end-to-end root mean-square distance, probability of end-toend
contact formation and intrachain diffusion coefficient. The data can be coherently interpreted on the basis of a simple chain
model with backbone angles obtained from a library of coil segments of proteins and hard sphere repulsion at each Ca position. In
buffered water, we find that introducing charges in a glycine-rich sequence induces a mild chain swelling and a significant speedup
of the intrachain dynamics, whereas the removal of the glycines results in almost a two-fold increase of the chain volume and
a drastic slowing down. In denaturants we observe a pronounced swelling of all the chains, with significant differences between
the effect of urea and guanidinium chloride.
Tipologia IRIS:
01 - Articolo su periodico
Keywords:
single-molecule fluorescence ; unfolded polypeptide-chains ; loop formation ; energy-transfer ; spectroscopic ruler ; denatured protein ; electron-transfer ; amino-acids ; dynamics ; rates ; peptides ; proteins ; tryptophan ; contact formation ; phosphorescence ; end-to-end distance ; FRET
Elenco autori:
A. Soranno, R. Longhi, T. Bellini, M. Buscaglia
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