Thermal stabilities of brain spectrin and the constituent repeats of subunits

An, Xiuli and Zhang, Xihui and Salomao, Marcela and Guo, Xinhua and Yang, Y. and Wu, Yu and Gratzer, Walter B. and Baines, Anthony J. and Mohandas, Narla (2006) Thermal stabilities of brain spectrin and the constituent repeats of subunits. Biochemistry, 45 (45). pp. 13670-13676. ISSN 0006-2960. (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided)

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The different genes that encode mammalian spectrins give rise to proteins differing in their apparent stiffness. To explore this, we have compared the thermal stabilities of the structural repeats of brain spectrin subunits (alphaII and betaII) with those of erythrocyte spectrin (alphaI and betaI). The unfolding transition midpoints (T(m)) of the 36 alphaII- and betaII-spectrin repeats extend between 24 and 82 degrees C, with an average higher by some 10 degrees C than that of the alphaI- and betaI-spectrin repeats. This difference is reflected in the T(m) values of the intact brain and erythrocyte spectrins. Two of three tandem-repeat constructs from brain spectrin exhibited strong cooperative coupling, with elevation of the T(m) of the less stable partner corresponding to coupling free energies of approximately -4.4 and -3.5 kcal/mol. The third tandem-repeat construct, by contrast, exhibited negligible cooperativity. Tandem-repeat mutants, in which a part of the "linker" helix that connects the two domains was replaced with a corresponding helical segment from erythroid spectrin, showed only minor perturbation of the thermal melting profiles, without breakdown of cooperativity. Thus, the linker regions, which tolerate few point mutations without loss of cooperative function, have evidently evolved to permit conformational coupling in specified regions. The greater structural stability of the repeats in alphaII- and betaII-spectrin may account, at least in part, for the higher rigidity of brain compared to erythrocyte spectrin.

Item Type: Article
Subjects: Q Science
Divisions: Faculties > Science Technology and Medical Studies > School of Biosciences > Cell & Developmental Biology Group
Depositing User: Anthony Baines
Date Deposited: 05 Sep 2008 06:23
Last Modified: 15 Apr 2014 15:33
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