Radiation-inactivation analysis of the Na+/bile acid co-transport system from rabbit ileum

The functional-unit molecular size of the Na+/bile acid cotransport system and the apparent target size of the bile-acid-binding proteins in brush-border membrane vesicles from rabbit ileum were determined by radiation inactivation with high-energy electrons. The size of the functional transporting unit for Na(+)-dependent taurocholate uptake was determined to 451 +/- 35 kDa, whereas an apparent molecular mass of 434 +/- 39 kDa was measured for the Na(+)-dependent D-glucose transport system. Proteins of 93 kDa and 14 kDa were identified as putative protein components of the ileal Na+/bile acid cotransporter in the rabbit ileum, whereas a protein of 87 kDa may be involved in passive intestinal bile acid uptake. Photoaffinity labelling with 3- and 7-azi-derivatives of taurocholate revealed a target size of 229 +/- 10 kDa for the 93 kDa protein, and 132 +/- 23 kDa for the 14 kDa protein. These findings indicate that the ileal Na+/bile acid co-transport system is in its functional state a protein complex composed of several subunits. The functional molecular sizes for Na(+)-dependent transport activity and the bile-acid-binding proteins suggest that the Na+/bile acid co-transporter from rabbit ileum is a homotetramer (AB)4 composed of four AB subunits, where A represents the integral 93 kDa and B the peripheral 14 kDa brush-border membrane protein.

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Characterization and chemical modification of the Na+-dependent bile-acid transport system in brush-border membrane vesicles from rabbit ileum

Biochimica et Biophysica Acta (BBA) - Biomembranes ◽

10.1016/0005-2736(92)90278-t ◽

1992 ◽

Vol 1111 (1) ◽

pp. 93-102 ◽

Cited By ~ 31

Author(s):

Werner Kramer ◽

Sven-Boris Nicol ◽

Frank Girbig ◽

Ulrike Gutjahr ◽

Simone Kowalewski ◽

...

Keyword(s):

Bile Acid ◽

Chemical Modification ◽

Transport System ◽

Brush Border ◽

Brush Border Membrane ◽

Membrane Vesicles ◽

Brush Border Membrane Vesicles ◽

Acid Transport ◽

Rabbit Ileum ◽

Bile Acid Transport

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Primary bile acid diarrhoea without an ileal carrier defect: quantification of active bile acid transport across the ileal brush border membrane.

Gut ◽

10.1136/gut.32.5.500 ◽

1991 ◽

Vol 32 (5) ◽

pp. 500-503 ◽

Cited By ~ 32

Author(s):

A J van Tilburg ◽

F W de Rooij ◽

J W van den Berg ◽

M van Blankenstein

Keyword(s):

Bile Acid ◽

Brush Border ◽

Brush Border Membrane ◽

Acid Transport ◽

Bile Acid Transport ◽

Defect Quantification ◽

Primary Bile Acid

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Identification of the taurine binding proteins from human placental brush border membrane

Placenta ◽

10.1016/0143-4004(91)90374-o ◽

1991 ◽

Vol 12 (4) ◽

pp. 382

Keyword(s):

Brush Border ◽

Binding Proteins ◽

Brush Border Membrane

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Intestinal cholesterol absorption: identification of different binding proteins for cholesterol and cholesterol absorption inhibitors in the enterocyte brush border membrane

Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids ◽

10.1016/s1388-1981(03)00068-4 ◽

2003 ◽

Vol 1633 (1) ◽

pp. 13-26 ◽

Cited By ~ 24

Author(s):

Werner Kramer ◽

Frank Girbig ◽

Daniel Corsiero ◽

Katja Burger ◽

Falk Fahrenholz ◽

...

Keyword(s):

Brush Border ◽

Binding Proteins ◽

Brush Border Membrane ◽

Cholesterol Absorption ◽

Intestinal Cholesterol Absorption

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Effect of pH on phosphate transport in rat renal brush border membrane vesicles

AJP Renal Physiology ◽

10.1152/ajprenal.1985.248.5.f705 ◽

1985 ◽

Vol 248 (5) ◽

pp. F705-F710 ◽

Cited By ~ 6

Author(s):

M. Amstutz ◽

M. Mohrmann ◽

P. Gmaj ◽

H. Murer

Keyword(s):

Transport System ◽

Brush Border ◽

Brush Border Membrane ◽

Phosphate Uptake ◽

Membrane Vesicles ◽

Brush Border Membrane Vesicles ◽

Effect Of Ph ◽

High Sodium ◽

Renal Brush Border Membrane ◽

Renal Brush Border

The initial linear rate of phosphate uptake was analyzed in rat renal brush border membrane vesicles. An increase in medium pH from 6.0 to 8.0 increased the sodium gradient-dependent phosphate uptake about 20-fold. Sodium-independent phosphate uptake was not altered in this pH range. At pH 7.4 an intravesicular acid pH stimulated the initial linear uptake rate (20-25%). The apparent Km for sodium increased from about 100 to 200 mM when pH was decreased from 7.4 to 6.4. The Hill coefficient for sodium interaction was close to 2 and was unaffected by pH. Increasing external sodium reduced the apparent Km of the transport system for phosphate independent of pH. Variations of phosphate concentration had no influence on the apparent Km for sodium. At high sodium concentrations, small effects (20-30%) of pH on the apparent Vmax of the transport system were found; measured at saturating sodium concentrations, the apparent Km values calculated on the basis of total phosphate were increased (50-60%) when pH was decreased from 7.4 to 6.4. The data indicate that the major effect of pH is to modify the interaction of the transport system with sodium. At nonsaturating sodium concentrations, this resulted indirectly in a reduction in the affinity for phosphate related to a different occupancy of the sodium binding site. The differences of transport rate at low phosphate and high sodium concentrations could be explained by preferential transport of divalent phosphate as well as by pH effects on other carrier properties.

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