Probing the urea dependence of residual structure in denatured human α-lactalbumin
| Autor: | Raffaella Ugolini, Lorna J. Smith, Heike I. Rösner, Christina Redfield, Victoria A. Higman, Lesley H. Greene |
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| Rok vydání: | 2009 |
| Předmět: |
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Molecular Protein Denaturation Protein Folding Chemistry & allied sciences Denatured state Residual dipolar couplings 010402 general chemistry 01 natural sciences Biochemistry Article 03 medical and health sciences chemistry.chemical_compound Humans Urea Reduced spectral density mapping Nuclear Magnetic Resonance Biomolecular Spectroscopy 030304 developmental biology Alanine Lactalbumin 0303 health sciences Nitrogen Isotopes Relaxation (NMR) Molten globule 0104 chemical sciences Folding (chemistry) Crystallography chemistry Protein folding 15N relaxation Hydrophobic and Hydrophilic Interactions Human α-lactalbumin Cysteine |
| Zdroj: | Journal of Biomolecular Nmr |
| ISSN: | 1573-5001 0925-2738 |
| Popis: | Backbone 15N relaxation parameters and 15N–1HN residual dipolar couplings (RDCs) have been measured for a variant of human α-lactalbumin (α-LA) in 4, 6, 8 and 10 M urea. In the α-LA variant, the eight cysteine residues in the protein have been replaced by alanines (all-Ala α-LA). This protein is a partially folded molten globule at pH 2 and has been shown previously to unfold in a stepwise non-cooperative manner on the addition of urea. 15N R2 values in some regions of all-Ala α-LA show significant exchange broadening which is reduced as the urea concentration is increased. Experimental RDC data are compared with RDCs predicted from a statistical coil model and with bulkiness, average area buried upon folding and hydrophobicity profiles in order to identify regions of non-random structure. Residues in the regions corresponding to the B, D and C-terminal 310 helices in native α-LA show R2 values and RDC data consistent with some non-random structural propensities even at high urea concentrations. Indeed, for residues 101–106 the residual structure persists in 10 M urea and the RDC data suggest that this might include the formation of a turn-like structure. The data presented here allow a detailed characterization of the non-cooperative unfolding of all-Ala α-LA at higher concentrations of denaturant and complement previous studies which focused on structural features of the molten globule which is populated at lower concentrations of denaturant. Electronic supplementary material The online version of this article (doi:10.1007/s10858-009-9342-y) contains supplementary material, which is available to authorized users. |
| Databáze: | OpenAIRE |
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