Probing the urea dependence of residual structure in denatured human α-lactalbumin
Backbone <sup>15</sup>N relaxation parameters and <sup>15</sup>N-<sup>1</sup>N<sup>N</sup> 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 cystein...
| Main Authors: | , , , , , |
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| Format: | Journal article |
| Language: | English |
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Springer
2009
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| _version_ | 1826261435912552448 |
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| author | Higman, V Rösner, H Ugolini, R Greene, L Redfield, C Smith, L |
| author_facet | Higman, V Rösner, H Ugolini, R Greene, L Redfield, C Smith, L |
| author_sort | Higman, V |
| collection | OXFORD |
| description | Backbone <sup>15</sup>N relaxation parameters and <sup>15</sup>N-<sup>1</sup>N<sup>N</sup> 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 In the α-LA variant, the eight cysteine residues in the protein have been replaced by alanines (all-Ala α-LA).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. <sup>15</sup>N R<sub>2</sub> 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 3<sub>10</sub> helices in native α-LA show R<sub>2</sub> values and RDC data consistent with some non-random structural propensities even a 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. |
| first_indexed | 2024-03-06T19:21:25Z |
| format | Journal article |
| id | oxford-uuid:1a37dfff-c48b-415a-8b74-aecb33bf29a1 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-06T19:21:25Z |
| publishDate | 2009 |
| publisher | Springer |
| record_format | dspace |
| spelling | oxford-uuid:1a37dfff-c48b-415a-8b74-aecb33bf29a12022-03-26T10:53:35ZProbing the urea dependence of residual structure in denatured human α-lactalbuminJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:1a37dfff-c48b-415a-8b74-aecb33bf29a1BiochemistryChemistry & allied sciencesEnglishOxford University Research Archive - ValetSpringer2009Higman, VRösner, HUgolini, RGreene, LRedfield, CSmith, LBackbone <sup>15</sup>N relaxation parameters and <sup>15</sup>N-<sup>1</sup>N<sup>N</sup> 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. <sup>15</sup>N R<sub>2</sub> 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 3<sub>10</sub> helices in native α-LA show R<sub>2</sub> values and RDC data consistent with some non-random structural propensities even a 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. |
| spellingShingle | Biochemistry Chemistry & allied sciences Higman, V Rösner, H Ugolini, R Greene, L Redfield, C Smith, L Probing the urea dependence of residual structure in denatured human α-lactalbumin |
| title | Probing the urea dependence of residual structure in denatured human α-lactalbumin |
| title_full | Probing the urea dependence of residual structure in denatured human α-lactalbumin |
| title_fullStr | Probing the urea dependence of residual structure in denatured human α-lactalbumin |
| title_full_unstemmed | Probing the urea dependence of residual structure in denatured human α-lactalbumin |
| title_short | Probing the urea dependence of residual structure in denatured human α-lactalbumin |
| title_sort | probing the urea dependence of residual structure in denatured human α lactalbumin |
| topic | Biochemistry Chemistry & allied sciences |
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