Nip-taurine and nap-taurine bind to the external modifier site of
ae1 (band 3), at which iodide inhibits anion exchange.
Knauf, Philip A., and Laurie J. Spinelli.
Department of Biophysics, University of Rochester School of
Medicine, Rochester, NY 14642
APStracts 2:0092C, 1995.
External iodide (Io) inhibits AE1(band 3)-mediated anion exchange in
human red blood cells by binding to a noncompetitive inhibitory site,
the external halide modifier site. External NAP-taurine (N-(4-azido
-2-nitrophenyl)-2-aminoethyl sulfonate) and NIP-taurine (N-(4
-isothiocyano-2-nitrophenyl)-2-aminoethyl sulfonate) also inhibit Cl-
exchange noncompetitively. Increasing Io decreases the inhibitory
potency of NIP-taurine in a competitive fashion; this effect is not
due to I- binding to the transport site, which has little effect on
the NIP-taurine affinity. BSSS (bis(sulfosuccinimidyl)-suberate)
abolishes the noncompetitive inhibitory effect of external iodide,
and greatly reduces the inhibitory effect of NAP-taurine. Together
with previous work, these data suggest that external halides such as
I-, Br-, and probably also Cl- bind to the same noncompetitive
inhibitory site as do NAP-and NIP-taurine, and that these reagents
can be used to label the halide modifier site. Lys-539, a probable
reaction site of BSSS, lies within the same segment of AE1 that is
labeled by NAP-taurine, and thus may be part of the modifier site.
Received 2 November 1994; accepted in final form 13 January 1995.
APS Manuscript Number C656-4.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 28 February 1995.