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 language||English (US)|
|Number of pages||3|
|Journal||Journal of Biological Chemistry|
|State||Published - Jan 7 1994|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology