Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

Backbone (15)N relaxation parameters and (15)N-(1)H(N) residual dipolar couplings (RDCs) have been measured for a variant of human alpha-lactalbumin (alpha-LA) in 4, 6, 8 and 10 M urea. In the alpha-LA variant, the eight cysteine residues in the protein have been replaced by alanines (all-Ala alpha-LA).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. (15)N R(2) values in some regions of all-Ala alpha-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(10) helices in native alpha-LA show R(2) 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 alpha-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.

Original publication




Journal article


J Biomol NMR

Publication Date





121 - 131


Alanine, Humans, Hydrophobic and Hydrophilic Interactions, Lactalbumin, Models, Molecular, Nitrogen Isotopes, Nuclear Magnetic Resonance, Biomolecular, Protein Denaturation, Protein Folding, Urea