title: Aromatic Cluster Sensor of Protein Folding: Near-UV Electronic Circular Dichroism Bands Assigned to Fold Compactness.
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 222 nm reporting secondary structural variations (far-UV range), Lbbands (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" Trp↔Tyr 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 folding↔unfolding mechanism. We found that the Lb293band 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 Trp↔Tyr 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.
authors: MTA-ELTE Protein Modelling Research Group, Eötvös Loránd University, Pázmány P. sétány 1A, 1117, Budapest, Hungary.
authors: Viktor
authors: http://orcid.org/0000-0002-8815-2783
authors: V
authors: Farkas
authors: MTA-ELTE Protein Modelling Research Group, Eötvös Loránd University, Pázmány P. sétány 1A, 1117, Budapest, Hungary.
authors: Imre
authors: I
authors: Jákli
authors: Department of Medical Chemistry, University of Szeged, Dóm tér 8, 6720, Szeged, Hungary.
authors: Gábor K
authors: GK
authors: Tóth
authors: MTA-ELTE Protein Modelling Research Group, Eötvös Loránd University, Pázmány P. sétány 1A, 1117, Budapest, Hungary. perczel@chem.elte.hu.|Laboratory of Structural Chemistry and Biology, Institute of Chemistry, Eötvös Loránd University, Pázmány P. sétány 1A, 1117, Budapest, Hungary. perczel@chem.elte.hu.
authors: András
authors: A
authors: Perczel
mesh_terms: D000595:Amino Acid Sequence; D002942:Circular Dichroism / Q000379:methods*; D004583:Electrons; D008958:Models, Molecular; D011487:Protein Conformation; D017510:Protein Folding; D055550:Protein Stability; D011506:Proteins / Q000737:chemistry*; D013696:Temperature; D014364:Tryptophan / Q000737:chemistry*; D014443:Tyrosine / Q000737:chemistry*
chemical_list: D011506:Proteins; D014443:Tyrosine; D014364:Tryptophan
keywords: Electronic circular dichroism spectra; Trp-Tyr interacting residues; folding intermediates; sensors; thermal unfolding