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Interaction of facilitative glucose transporter with glucokinase and its modulation by ADP and glucose‐6‐phosphate
Author(s) -
Lachaal Mohsen,
Jung Chan Y.
Publication year - 1993
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041560215
Subject(s) - glucokinase , intracellular , vesicle , biochemistry , chemistry , transporter , glucose transporter , binding site , enzyme , binding protein , biophysics , conformational change , biology , endocrinology , insulin , membrane , gene
Bacterial glucokinase (GK) binds to purified, human erythrocyte glucose transporter (GT) reconstituted in vesicles. The binding is largely abolished if GT is predigested with trypsin, indicating that GK binds to the cytoplasmic domain of GT. The binding is a saturable function of GK concentration showing two distinct affinities with apparent K D of 0.33 and 5.1 μM. The binding is stimulated by an increasing concentration of ADP with the 50% maximal effect at 5 mM. Glucose‐6‐phosphate (G6P) also stimulates the binding with a distinct optimum at 25 mM. The binding is stimulated only slightly by ATP. D‐glucose has no affect on the binding. KCl enhances the binding with the maximal effect at physiological intracellular concentrations. The binding is sensitive to changes in pH with an optimum at pH 4. The binding causes no detectable functional change in GT. However, the enzymatic activity of GK measured at nanomolar concentrations of GK is significantly greater in the presence of GT vesicles than in its absence or in the presence of protein‐free vesicles, indicating that GK interacts with GT at this low concentration range with an apparent K D of 10 mM. Although its physiological significance is not known, the GK‐GT interaction in vitro described here suggests that these two proteins may also interact in the cell and regulate carbohydrate metabolism. © 1993 Wiley‐Liss, Inc.