Calorimetric evidence for allosteric subunit interactions associated with inhibitor binding to band 3 transporter

Heidi M. Van Dort, Philip S. Low, Karen A. Cordes, Lawrence M. Schopfer, James M. Salhany

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21 Scopus citations


A calorimetric endotherm occurring at 68 °C (the C-transition) has been assigned previously to the integral domain of band 3 and was shown to be shifted to 78 °C after covalent binding of 4,4'-diisothiocyanostilbene- 2,2'-disulfonate (DIDS). In this study, we correlate the fractional appearance of the shifted C-transition with the fraction of DIDS bound to the band 3 monomer population. Our results show a distinctly nonlinear correlation plot with the appearance of the shifted C-transition lagging behind DIDS labeling of the band 3 monomer population. The lag suggests that both monomers of a band 3 dimer must be labeled by DIDS in order for the shifted C-transition to appear at 78 °C, implying that the thermal unfolding of the integral domain of band 3 is modulated by allosteric interactions between subunits. This is the first in situ structural evidence supporting ligand-mediated subunit interactions within a 'carrier'-type transporter protein oligomer.

Original languageEnglish (US)
Pages (from-to)59-61
Number of pages3
JournalJournal of Biological Chemistry
Issue number1
Publication statusPublished - Jan 7 1994


ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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