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Kinetics of DIDS Inhibition of HL-60 Cell Anion Exchange Rules Out Ping-Pong Model With Slippage

Kinetics of DIDS Inhibition of HL-60 Cell Anion Exchange Rules Out Ping-Pong Model With Slippage

D Restrepo, B L Cronise, R B Snyder, L J Spinelli, P A Knauf

Am J Physiol. 1991 Mar;260(3 Pt 1):C535-44.

PMID: 1848401

Abstract:

According to the ping-pong model of band 3-mediated anion exchange, the transport protein has a single transport site, which can exist in either an inward-facing or an outward-facing conformation. Anions bind to these unloaded forms of the carrier, and translocation takes place only when a suitable anion is bound to the transport site. In a previous paper [Am. J. Physiol. 257 (Cell Physiol. 26): C520-C527, 1989], we had shown that the substrate kinetics of Cl-Cl exchange in the promyelocytic HL-60 cell cannot be explained by this simple ping-pong model of anion exchange but is consistent with a simultaneous model according to which both extracellular and intracellular anions must bind before simultaneous translocation can take place. In the present paper we show that external 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) inhibits anion exchange in HL-60 cells by competing with Cl- for binding to the outward-facing transport site. Furthermore, there is a linear dependence of the slope of the Dixon plot for inhibition by DIDS on the reciprocal of the intracellular Cl- concentration. This result clearly rules out a simple ping-pong scheme. In addition, the data also rule out a ping-pong model in which some translocation of the unloaded carrier is allowed (ping-pong model with slippage). The observed inhibition kinetics can be modeled by a simultaneous model of Cl-Cl exchange with competitive inhibition by DIDS.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP192718062	C527		192718-06-2	Price

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