Aromatic Cluster Sensor of Protein Folding: Near-UV Electronic Circular Dichroism Bands Assigned to Fold Compactness.
Chemistry
; 22(39): 13871-13883, 2016 Sep 19.
Article
em En
| MEDLINE
| ID: mdl-27504963
ABSTRACT
Both far- and near-UV electronic circular dichroism (ECD) spectra have bands sensitive to thermal unfolding of Trp and Tyr residues containing proteins. Beside spectral changes at 222â
nm reporting secondary structural variations (far-UV range), Lb bands (near-UV range) are applicable as 3D-fold sensors of protein's core structure. In this study we show that both Lb (Tyr) and Lb (Trp) ECD bands could be used as sensors of fold compactness. ECD is a relative method and thus requires NMR referencing and cross-validation, also provided here. The ensemble of 204 ECD spectra of Trp-cage miniproteins is analysed as a training set for "calibrating" TrpâTyr folded systems of known NMR structure. While in the far-UV ECD spectra changes are linear as a function of the temperature, near-UV ECD data indicate a non-linear and thus, cooperative unfolding mechanism of these proteins. Ensemble of ECD spectra deconvoluted gives both conformational weights and insight to a protein foldingâunfolding mechanism. We found that the Lb293 band is reporting on the 3D-structure compactness. In addition, the pure near-UV ECD spectrum of the unfolded state is described here for the first time. Thus, ECD folding information now validated can be applied with confidence in a large thermal window (5≤T≤85 °C) compared to NMR for studying the unfolding of TrpâTyr residue pairs. In conclusion, folding propensities of important proteins (RNA polymerase II, ubiquitin protein ligase, tryptase-inhibitor etc.) can now be analysed with higher confidence.
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MEDLINE
Assunto principal:
Tirosina
/
Triptofano
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Proteínas
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Dicroísmo Circular
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Dobramento de Proteína
Idioma:
En
Ano de publicação:
2016
Tipo de documento:
Article