The irreversible inhibition of glucose transport by 1-fluoro-2,4-dinitrobenzene (FDNB) has been used to identify membrane proteins possibly associated with glucose transport in human crythrocytes. D-Glucose was shown to enhance significantly the rate of FDNB inhibition of transport when present during the reaction, whereas cytochalasin B (CB) and D-maltose retarded this FDNB inhibition of transport. This modulation of the inhibition reaction formed the basis for a double isotopic differential labeling technique using [14C]- and [3H]FDNB followed by SDS-polyacrylamide gel electrophoresis to distinguish transport-associated polypeptides from bulk membrane dinitrophenylated proteins.Reactions in the presence of CB or maltose revealed the presence of a differentially labeled polypeptide(s), with a molecular weight of approximately 60,000-65,000 daltons. This effect could in part be reversed in the presence of D-glucose but not L-glucose. Reactions in the presence of D-glucose resulted in two regions of differ...

Differential labeling of components in human erythrocyte membranes associated with the transport of glucose

Photolabeling of the adipocyte hexose carrier with an aryl azide derivative of maltose

L’effet des vitamines B12, B9 et B6 sur la fragilite osmotique des erythrocytes humains a ete explore in vitro . De fortes concentrations de vitamines B12 et B6 ont protege les erythrocytes de l’hemolyse hypotonique, avec une protection maxima atteinte respectivement a 10 et 500 µg/ml. A concentrations plus faibles, cependant, ces vitamines ont favorise grandement l’hemolyse hypotonique. Par contre, la vitamine B9 a montre uniquement un effet hemolytique de 4 a 200 µg/ml. Cet effet peut etre explique par la nature acide de la molecule. L’effet nul sur la fragilite osmotique de deux vitamines antagonistes, peut probablement etre explique par l’antagonisme partiel ou par la presence de ces deux vitamines simultanement: ces dernieres se lient en quantites appreciables a la cellule intacte de meme qu’a l’hemolysat et il y’ a competition mutuelle entre ces vitamines et leur transport.

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Effet des vitamines b12, b9 et b6 et leurs interactions sur la fragilite osmotique des erythrocytes humains

Disaccharides (sucrose, lactose, melibiose, cellobiose, trehalose, maltose, and isomaltose) are not transported across the human erythrocyte membrane. Maltose alone is bound in appreciable amounts to the intact cell as well as ghost membranes and competes mutually for uptake with D-glucose. In (NH4)2SO4-precipitated membrane preparations, maltose binds more strongly than other disaccharides (KD = 1.3 × 10−5 M; maximum binding capacity, 71 pmol/mg protein) and again competes mutually with D-glucose. Phloretin inhibits the binding of glucose much more than that of maltose.

Ivan Beneš

Papers

Uptake and binding of disaccharides in human erythrocytes