Organization and dynamics of tryptophans in the molten globule state of bovine α -lactalbumin utilizing wavelength-selective fluorescence approach: comparisons with native and denatured states

Chaudhuri, Arunima ; Haldar, Sourav ; Chattopadhyay, Amitabha (2010) Organization and dynamics of tryptophans in the molten globule state of bovine α -lactalbumin utilizing wavelength-selective fluorescence approach: comparisons with native and denatured states Biochemical and Biophysical Research Communications, 394 (4). pp. 1082-1086. ISSN 0006-291X

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Official URL: http://linkinghub.elsevier.com/retrieve/pii/S00062...

Related URL: http://dx.doi.org/10.1016/j.bbrc.2010.03.130

Abstract

Bovine a-lactalbumin (BLA) is known to be present in molten globule form in its apo-state (i.e., Ca2+ depleted state). We explored the organization and dynamics of the functionally important tryptophan residues of BLA in native, molten globule and denatured states utilizing the wavelength-selective fluorescence approach. We observed red edge excitation shift (REES) of 7 nm for the tryptophans in native BLA. Interestingly, we show here that BLA tryptophans exhibit considerable REES (8 nm) in its molten globule state. Taken together, these results indicate that tryptophan residues in BLA in native as well as molten globule states experience motionally restricted environment. We further show that even the denatured form of BLA exhibits a modest REES of 3 nm, indicating that the tryptophans are shielded from bulk solvent, even when denatured, due to the presence of residual structure around tryptophan(s). This is further supported by wavelength-dependent changes in fluorescence anisotropy and lifetime for BLA tryptophans. These novel results constitute one of the first reports of REES in the molten globule state of proteins, and could provide vital insight into the role of tryptophans in the function of BLA in its molten globule state in particular, and other partially ordered proteins in general.

Item Type:Article
Source:Copyright of this article belongs to Elsevier Science.
Keywords:Molten Globule; α-lactalbumin; Red Edge Excitation Shift; Protein Conformation; Fluorescence Anisotropy; Fluorescence Lifetime
ID Code:7236
Deposited On:25 Oct 2010 12:05
Last Modified:16 May 2016 17:28

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