Skip to main content

Spectrin alpha II and beta II isoforms interact with high affinity at the tetramerization site.

Bignone, Paola A., Baines, Anthony J. (2003) Spectrin alpha II and beta II isoforms interact with high affinity at the tetramerization site. Biochemical Journal, 374 . pp. 613-624. ISSN 0264-6021. (doi:10.1042/BJ20030507) (Access to this publication is currently restricted. You may be able to access a copy if URLs are provided) (KAR id:13)

Language: English

Restricted to Repository staff only
[thumbnail of Bignone_&_Baines_2003,_Biochem_J.pdf]
Official URL:


Spectrin tetramers form by the interaction of two alpha-beta dimers through two helices close to the C-terminus of a beta subunit and a single helix at the N-terminus of an alpha subunit. Early work on spectrin from solid tissues (typified by alphaII and betaII polypeptides) indicated that it forms a more stable tetramer than erythroid spectrin (alphaI-betaI). In the present study, we have probed the molecular basis of this phenomenon. We have quantified the interactions of N-terminal regions of two human alpha polypeptides (alphaI and alphaII) with the C-terminal regions of three beta isoforms (betaISigma1, betaIISigma1 and betaIISigma2). alphaII binds either betaII form with a much higher affinity than alphaI binds betaISigma1 ( K (d) values of 5-9 nM and 840 nM respectively at 25 degrees C). betaIISigma1 and betaIISigma2 are splice variants with different C-terminal extensions outside the tetramerization site: these extensions affect the rate rather than the affinity of alpha subunit interaction. alphaII spectrin interacts with each beta subunit with higher affinity than alphaI, and the betaII polypeptides have higher affinities for both alpha chains than betaISigma1. The first full repeat of the alpha subunit has a major role in determining affinity. Enthalpy changes in the alphaII-betaIISigma2 interaction are large, but the entropy change is comparatively small. The interaction is substantially reduced, but not eliminated, by concentrated salt solutions. The high affinity and slow overall kinetics of association and dissociation of alphaII-betaII spectrin may suit it well to a role in strengthening cell junctions and providing stable anchor points for transmembrane proteins at points specified by cell-adhesion molecules.

Item Type: Article
DOI/Identification number: 10.1042/BJ20030507
Subjects: Q Science
Divisions: Divisions > Division of Natural Sciences > Biosciences
Depositing User: Susan Davies
Date Deposited: 19 Dec 2007 17:43 UTC
Last Modified: 16 Nov 2021 09:38 UTC
Resource URI: (The current URI for this page, for reference purposes)
  • Depositors only (login required):

Total unique views for this document in KAR since July 2020. For more details click on the image.