Mode of Insertion of the Sucrase-Isomaltase Complex in the Intestinal Brush Border Membrane: Implications for the Biosynthesis of this Stalked Intrinsic Membrane Protein

2008 ◽  
pp. 133-146 ◽  
Author(s):  
G. Semenza
Keyword(s):  
Membrane Protein ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Intestinal Brush Border Membrane ◽  
Intestinal Brush Border

scholarly journals Structural Determinants Required for Apical Sorting of an Intestinal Brush-border Membrane Protein

2000 ◽  
Vol 275 (9) ◽  
pp. 6566-6572 ◽  
Author(s):  
Ralf Jacob ◽  
Marwan Alfalah ◽  
Jürgen Grünberg ◽  
Maik Obendorf ◽  
Hassan Y. Naim
Keyword(s):  
Membrane Protein ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Structural Determinants ◽  
Intestinal Brush Border Membrane ◽  
Intestinal Brush Border ◽  
Apical Sorting

Divalent cations and vitamin B12 uptake by intestinal brush-border membrane vesicles

1980 ◽  
Vol 239 (6) ◽  
pp. G452-G456
Author(s):  
R. C. Beesley ◽  
C. D. Bacheller
Keyword(s):  
Vitamin B12 ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Divalent Cations ◽  
Intrinsic Factor ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Tetraacetic Acid ◽  
Intestinal Brush Border Membrane ◽  
Intestinal Brush Border

Brush-border membrane vesicles from hamster intestine were employed to investigate uptake (binding) of vitamin B12 (B12). Ileal vesicles took up 25 times more B12 than did jejunal vesicles. Uptake of B12 by ileal vesicles was dependent on intrinsic factor (IF) and required Ca2+. Increasing the Ca2+ concentration caused an increase in uptake of B12 reaching a maximum at approximately 8 mM Ca2+. At high Ca2+ concentrations, 6–8 mM, Mg2+ had little effect on uptake of B12. At low Ca2+ concentrations, up to 2 mM, Mg2+ stimulated B12 uptake. Mg2+, Mn2+, and, to a lesser extent, Sr2+ stimulated Ca2+-dependent B12 uptake, but Zn2+, Ba2+, Na+, K+, and La3+ did not. B12 was apparently not metabolized and was bound as IF-B12 complex, which could be removed with (ethylenedinitrilo)tetraacetic acid (EDTA). Our results suggest that two types of divalent cation reactive sites are involved in binding of IF-B12. One is Ca2+ specific. The other is less specific reacting with Mg2+, Mn2+, Sr2+, and perhaps Ca2+ itself, thereby stimulating Ca2+-dependent binding of IF-B12 to its ileal receptor.

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