Fluorine-19 NMR studies of glucosyl fluoride transport in human erythrocytes.
Fluorine-19 magnetization transfer studies have been used to measure the transport rate of glucopyranosyl fluorides under equilibrium exchange conditions. Although rate constants and permeabilities could be determined for beta-D-glucopyranosyl fluoride, the exchange rate for alpha-D-glucopyranosyl fluoride was found to be too slow for determination using this method. The time-dependent decomposition of the beta-glucopyranosyl fluoride also limits the accuracy of the numerical results for this species; however, it is clear that the permeabilities of the alpha and beta forms differ significantly, i.e., P beta > P alpha. This observation is in contrast to recent observations for n-fluoro-n-deoxyglucose, for which P alpha > P beta for n = 2, 3, 4, or 6. The difference can be explained in terms of a simple alternating conformation model in which one of the conformations (with an external sugar-binding site) exhibits a preference for the beta form of the molecule, while the second conformation (with an internal sugar binding site) exhibits a preference for the alpha form. Fluorine/hydroxyl substitutions unmask these preferences by selectively reducing the binding to one of the conformations, depending on the specific site of fluorination.
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Laboratory of Molecular Biophysics, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA.
Gabel
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D001665:Binding Sites; D001693:Biological Transport, Active; D055592:Biophysical Phenomena; D001703:Biophysics; D004912:Erythrocytes / Q000378:metabolism*; D005461:Fluorine / Q000737:chemistry; D005947:Glucose / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D009004:Monosaccharide Transport Proteins / Q000097:blood / Q000737:chemistry; D011487:Protein Conformation; D013237:Stereoisomerism
D009004:Monosaccharide Transport Proteins; C030364:glucosyl fluoride; D005461:Fluorine; D005947:Glucose