Cargando…

Titration of transport and modifier sites in the red cell anion transport system

This work demonstrates the existence of titratable transport and modifier sites in the anion transport system of human red cells. Effects of alkaline extracellular pH on chloride exchange were studied up to pH 13 at 0 degrees C. The studies revealed two sets of reversible titratable groups. One set,...

Descripción completa

Detalles Bibliográficos
Formato: Texto
Lenguaje:English
Publicado: The Rockefeller University Press 1982
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2215494/
https://www.ncbi.nlm.nih.gov/pubmed/6276496
_version_ 1782149029551931392
collection PubMed
description This work demonstrates the existence of titratable transport and modifier sites in the anion transport system of human red cells. Effects of alkaline extracellular pH on chloride exchange were studied up to pH 13 at 0 degrees C. The studies revealed two sets of reversible titratable groups. One set, having a pK of or approximately 11, appeared to be identical with the inhibitory halide-binding modifier site. Deprotonation of this site stimulated anion transport. The apparent dissociation constants of chloride and iodide at this modifier site were 0.3 and 0.06 M, respectively, and it was confirmed that the organic sulfonate NAP-taurine inhibits anion transport reversibly by a high-affinity interaction with halide-binding modifier sites at the extracellular side of the membrane. Other groups, with apparent pK of or approximately 12 at chloride concentrations above 0.1 M, were named as "transport sites" because transport function depended totally on their protonation. The apparent pK decreased when extracellular halide concentrations was lowered below 0.1 M. It was dependent of the intracellular chloride concentration, and was equally sensitive to extracellular pH of 13, was fully reversible. Hydroxyl ions were not transported to an appreciable extent by the anion exchange system. The pK values of both sets of groups make it likely that they are both arginyl residues, functioning as anion recognition sites similar to the role of functionally essential arginyl residues observed with numerous enzymes.
format Text
id pubmed-2215494
institution National Center for Biotechnology Information
language English
publishDate 1982
publisher The Rockefeller University Press
record_format MEDLINE/PubMed
spelling pubmed-22154942008-04-23 Titration of transport and modifier sites in the red cell anion transport system J Gen Physiol Articles This work demonstrates the existence of titratable transport and modifier sites in the anion transport system of human red cells. Effects of alkaline extracellular pH on chloride exchange were studied up to pH 13 at 0 degrees C. The studies revealed two sets of reversible titratable groups. One set, having a pK of or approximately 11, appeared to be identical with the inhibitory halide-binding modifier site. Deprotonation of this site stimulated anion transport. The apparent dissociation constants of chloride and iodide at this modifier site were 0.3 and 0.06 M, respectively, and it was confirmed that the organic sulfonate NAP-taurine inhibits anion transport reversibly by a high-affinity interaction with halide-binding modifier sites at the extracellular side of the membrane. Other groups, with apparent pK of or approximately 12 at chloride concentrations above 0.1 M, were named as "transport sites" because transport function depended totally on their protonation. The apparent pK decreased when extracellular halide concentrations was lowered below 0.1 M. It was dependent of the intracellular chloride concentration, and was equally sensitive to extracellular pH of 13, was fully reversible. Hydroxyl ions were not transported to an appreciable extent by the anion exchange system. The pK values of both sets of groups make it likely that they are both arginyl residues, functioning as anion recognition sites similar to the role of functionally essential arginyl residues observed with numerous enzymes. The Rockefeller University Press 1982-02-01 /pmc/articles/PMC2215494/ /pubmed/6276496 Text en This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/).
spellingShingle Articles
Titration of transport and modifier sites in the red cell anion transport system
title Titration of transport and modifier sites in the red cell anion transport system
title_full Titration of transport and modifier sites in the red cell anion transport system
title_fullStr Titration of transport and modifier sites in the red cell anion transport system
title_full_unstemmed Titration of transport and modifier sites in the red cell anion transport system
title_short Titration of transport and modifier sites in the red cell anion transport system
title_sort titration of transport and modifier sites in the red cell anion transport system
topic Articles
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2215494/
https://www.ncbi.nlm.nih.gov/pubmed/6276496