title: Calorimetric evidence for allosteric subunit interactions associated with inhibitor binding to band 3 transporter.
abstract: A calorimetric endotherm occurring at 68 degrees C (the C-transition) has been assigned previously to the integral domain of band 3 and was shown to be shifted to 78 degrees 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 degrees 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.
authors.affiliation: Department of Chemistry, Purdue University, West Lafayette, Indiana 47907.
authors.forename: H M
authors.initials: HM
authors.lastname: Van Dort
authors.forename: P S
authors.initials: PS
authors.lastname: Low
authors.forename: K A
authors.initials: KA
authors.lastname: Cordes
authors.forename: L M
authors.initials: LM
authors.lastname: Schopfer
authors.forename: J M
authors.initials: JM
authors.lastname: Salhany
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000378:metabolism / Q000494:pharmacology; D000495:Allosteric Site; D001457:Anion Exchange Protein 1, Erythrocyte / Q000037:antagonists & inhibitors* / Q000378:metabolism; D002151:Calorimetry; D006801:Humans; D013050:Spectrometry, Fluorescence
chemical_list: D001457:Anion Exchange Protein 1, Erythrocyte; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid