Falke, Joseph J. and Pace, R. J. and Chan, Sunney I. (1984) Chloride binding to the anion transport binding sites of band 3. A 35Cl NMR study. Journal of Biological Chemistry, 259 (10). pp. 6472-6480. ISSN 0021-9258. http://resolver.caltech.edu/CaltechAUTHORS:FALjbc84b
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Band 3 is an integral membrane protein that exchanges anions across the red cell membrane. Due to the abundance and the high turnover rate of the band 3 transport unit, the band 3 system is the most heavily used ion-transport system in a typical vertebrate organism. Here we show that 35Cl NMR enables direct and specific observation of substrate Cl- binding to band 3 transport sites, which are identified by a variety of criteria: (a) the sites are inhibited by 4,4'- dinitrostilbene -2,2'- disulfonate, which is known to inhibit competitively Cl- binding to band 3 transport sites; (b) the sites have affinities for 4,4'- dinitrostilbene -2,2'-disulfonate and Cl- that are quantitatively similar to the known affinities of band 3 transport sites for these anions; and (c) the sites have relative affinities for Cl-, HCO-3, F-, and I- that are quantitatively similar to the known relative affinities of band 3 transport sites for these anions. The 35Cl NMR assay also reveals a class of low affinity Cl- binding sites (KD much greater than 0.5 M) that are not affected by 4,4'- dinitrostilbene -2,2'- disulfonate. These low affinity sites may be responsible for the inhibition of band 3 catalyzed anion exchange that has been previously observed at high [Cl-]. In the following paper the 35Cl NMR assay is used to resolve the band 3 transport sites on opposite sides of the membrane, thereby enabling direct observation of the transmembrane recruitment of transport sites.
|Additional Information:||Copyright © 1984 by the American Society for Biochemistry and Molecular Biology. (Received for publication, September 13, 1983) This work was supported by National Institute of General Medical Sciences Grant GM-22432. Contribution 6887 from the Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, CA 91125. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. [J.J.F. was] [s]upported by a National Science Foundation Predoctoral Fellowship. Appendices I-III (including Figs. A1 and A2) are presented in miniprint at the end of this paper. Miniprint is easily read with the aid of a standard magnifying glass|
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