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Centrifugal and chromatographic analyses of tryptophan and tyrosine uptake by red blood cells and GLUT1 proteoliposomes with permeability estimates and observations on dihydrocytochalasin B
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry.
2003 (English)In: Journal of Biochemical and Biophysical Methods, ISSN 0165-022X, E-ISSN 1872-857X, Vol. 55, no 2, 127-140 p.Article in journal (Refereed) Published
Abstract [en]

We analyzed transport into liposomes and proteoliposomes, separated the free and internalized radioactively labeled substrates by size-exclusion chromatography (SEC) and observed a net influx owing to nonfacilitated diffusion across the lipid bilayers during the separation. The permeabilities (10(-9) cm/s) of glucose transporter (GLUT1) proteoliposomes were estimated to be 4.6, 1.0, 1.4 and 2.1 for D-glucose, L-glucose, L-Tyr and L-Trp, respectively; 15, 3.3, 5.1 and 2.1 times higher than the corresponding permeabilities of liposomes. These values indicated that GLUT1 did not transport Tyr or Trp, or transported Tyr, and only Tyr, slowly. This interpretation was supported by further analyses. Dihydrocytochalasin B inhibited the transport of Tyr and, partially, Trp into human red blood cells (centrifugal analyses). It did not inhibit Tyr and Trp influx into GLUT1 proteoliposomes, but partitioned strongly into the bilayers and seemed to make them fragile. The GLUT1 inhibitor cytochalasin B and the GLUT1 substrate 2-deoxy-D-glucose did not inhibit Tyr transport into the cells. Upon immobilized biomembrane affinity chromatography, Trp decreased the cytochalasin B retardation by GLUT1 only at levels far above the physiological Trp concentration. Ethanol (commonly added to aqueous solutions for enhancing a compound's solubility) halved the retardation at 4% (v/v) concentration. Drastic modification of the SEC method is required to allow permeability measurements with nonlabeled and highly permeable substrates.

Place, publisher, year, edition, pages
2003. Vol. 55, no 2, 127-140 p.
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:uu:diva-90677DOI: 10.1016/S0165-022X(02)00175-6PubMedID: 12628696OAI: oai:DiVA.org:uu-90677DiVA: diva2:163121
Available from: 2003-09-04 Created: 2003-09-04 Last updated: 2013-05-31Bibliographically approved
In thesis
1. Affinity-, Partition- and Permeability Properties of the Human Red Blood Cell Membrane and Biomembrane Models, with Emphasis on the GLUT1 Glucose Transporter
Open this publication in new window or tab >>Affinity-, Partition- and Permeability Properties of the Human Red Blood Cell Membrane and Biomembrane Models, with Emphasis on the GLUT1 Glucose Transporter
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The human glucose transporter GLUT1 is abundant in red blood cells, the blood-brain barrier and epithelial cells, where it mediates the transport of the energy metabolite, glucose. In the present work some properties of GLUT1, including affinity binding of both substrates and inhibitors, transport rates as well as permeabilities of aromatic amino acids and drug-membrane interactions were analyzed by chromatographic methods.

Reconstitution by size-exclusion chromatography on Superdex 75 from a detergent with a low CMC that provides monomeric GLUT1 was examined regarding D-glucose- and CB binding as well as D-glucose transport. Upon steric immobilization in Superdex 200 gel beads, residual detergent could be washed away and dissociation constants in the same range as reported for binding to GLUT1 reconstituted from other detergents were obtained. The transport rate into the GLUT1 proteoliposomes was low, probably due to residual detergent. Binding to GLUT1 at different pH was analyzed and the affinity of glucose and GLUT1 inhibitors was found to decrease with increasing pH (5–8.7). The average number of cytochalasin B-binding sites per GLUT1 monomers was, in most cases, approximately 0.4. GLUT1 may work as a functional monomer, dimer or oligomer. To determine whether GLUT1 was responsible for the transport of the aromatic amino acids tyrosine and tryptophan, uptake values and permeabilities of these amino acids into liposomes and GLUT1 proteoliposomes were compared to the permeabilities of D- and L- glucose in the same systems. Dihydrocytochalasin B was identified to be a new inhibitor of tyrosine and tryptophan transport into red blood cells. Ethanol turned out to inhibit the specific binding between CB and GLUT1 and also to decrease the partitioning of CB and drugs into lipid bilayers. A capacity factor for drug partitioning into membranes that allows comparison between columns with different amount of immobilized lipids was validated, and turned out to be independent of flow rate, amount of lipids and drug concentration in the ranges tested.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2003. 50 p.
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 868
Keyword
Biochemistry, Affinity, Aromatic amino acids, Binding, Biomembrane, Biotin, Chromatography, Cytochalasin B, Dihydrocytochalasin B, Dissociation constant, Drug absorption, Ethanol, Equilibrium, Glucose, GLUT1, Immobilization, Immobilized biomembrane affinity chromatography, Immobilized liposome chromatography, Interaction, Liposome, Membrane protein, Membrane vesicle, Partitioning, Phospholipid bilayer, Proteoliposome, Quantitative, Red blood cell, Specific, Streptavidin, Tyrosine, Tryptophan, Biokemi
National Category
Medical Biotechnology (with a focus on Cell Biology (including Stem Cell Biology), Molecular Biology, Microbiology, Biochemistry or Biopharmacy)
Identifiers
urn:nbn:se:uu:diva-3525 (URN)91-554-5692-8 (ISBN)
Public defence
2003-09-26, B:41, BMC, Husarvägen 3, 13:15
Opponent
Supervisors
Available from: 2003-09-04 Created: 2003-09-04 Last updated: 2013-06-10Bibliographically approved

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