Amiloride-binding proteins

Huot et al. [38] used affinity chromatography to identify and partially purify an amiloride-binding protein with characteristics of the renal brush border Na /H exchanger. The high-affinity amiloride analog A35 (5-A-(3-aminophenyl)amiloride) was coupled to Sepharose CL-4B through a triglycine spacer. Rabbit renal brush border membranes were solubilized with 0.6% Triton X-100, incubated with the... 

Subsequently, proteolytic fragments of the rabbit renal 25-kDa amiloride-binding protein were micro-sequenced and found to have high sequence homology with rat and human NAD(P)H quinone oxidoreductase. Indeed, enzymatic assays revealed that renal brush border membrane vesicles contain significant NADPH quinone oxidoreductase activity. Presumably NAD(P)H quinone oxidoreductase coincidentally binds amiloride analogs with the same rank order as the Na /H exchanger [39]. 

ABP1 Amiloride binding protein 1 (amine oxidase (copper-containing)) ABP, DAO, 7q34 - 7q36 KAO, AOC1, DAOl 150,180,506 -150,189,312 8807 5 2428 751... 

Barbry, P., Champe, M., Chassande, O., Munemitsu, S., Champigny, G., Lingueglia, E., Maes, P, Frelin, C., Tartar, A., Ullrich, A., and Lazdunski, M., 1990, Human kidney amiloride binding protein cDNA structure and functional expression, Proc. Natl. Acad. Sci. U. S. A. 87 734797351. 

Lingueglia, E., Renard, S., Voilley, N., Waldmann, R., Chassande, O., Lazdunski, M., and Barbry, P., 1993, Molecular cloning and functional expression of different molecular forms of rat amiloride binding proteins, Eur. J. Biochem. 216 679n687. 

Diamine oxidase occurs, like amine oxidase, in bacteria, animals, and plants [133]. The comparison of amino acid sequences of the amiloride-binding protein from human kidney, rat colon, diamine oxidase from human placenta, pig kidney, and amine oxidase from Hansenula polymorpha and lentil seeds has shown that the amiloride-binding protein and diamine oxidase are identical proteins[29]. The amiloride-binding protein was previously postulated to function as an epithelial sodium-transporter. While its physiological function is still... 

Recently, the cofactor peptides have also been isolated from semicarbazide-sensitive amine oxidases purified from bovine and porcine aortas [52], sequenced and confirmed to contain the topa quinone. The same topa quinone consensus sequence was also found in the primary structures of amine oxidases from human kidney [53], human retina [54] and rat colon [55], so called amiloride-binding proteins , and amine oxidase from human placenta [56] that shows 81% identity with bovine plasma amine oxidase [57], bovine lung amine oxidase [58], and amine oxidases from pea and lentil seedlings [59,60], chick pea seedlings [61], and Arabidopsis thaliana [62] obtained by the molecular cloning of respective DNAs. 

A35 affinity matrix, and eluted with various media. A 25-kDa protein bound to the affinity matrix and was completely eluted with 5 mM free amiloride. The abundance of the 25-kDa protein in brush border and basolateral membranes correlated closely with Na /H exchange activity. Importantly, binding of the 25-kDa protein to the affinity matrix was blocked by MIA > amiloride > benzamil, a rank order identical to that for inhibition of Na /H exchange activity, which suggested strongly that the 25-kDa protein was a structural component of the transporter. 

Many compounds that perturb the cellular cytoskeleton affect phagocytosis and macropinocytosis. Binding to actin filaments by the natural product cytochalasin D blocks both of these uptake mechanisms. Disruption of microtubules by the antimitotic agents colchicine and nocodazole inhibits macropinocytosis and affects some mechanisms of phagocytosis. The diuretic drug amiloride, which is an inhibitor of Na+/H+ antiporters, selectively blocks macropinocytosis. By activating protein kinase C, phorbol esters represent a class of small molecules that promote macropinocytosis. 

Spironolactone is highly protein bound. Triamterene has moderate protein binding. Amiloride has insignificant protein binding and a very large volume of distribution. 

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