Regulation of Na+-H+ exchange by transmethylation reactions in rat colonic brush-border membranes.
Incubation of rat colonic brush-border membrane vesicles with 200 microM S-adenosyl-L-[Me-3H]methionine resulted in the labeling of both membrane phospholipids and proteins. This labeling was decreased approximately 50% by the methylation inhibitor S-adenosyl-L-homocysteine (2 mM). Utilizing the pH-sensitive fluorescent dye, acridine orange, as a means of determining Na+-H+ exchange, S-adenosyl-L-methionine (200 microM) significantly increased sodium-stimulated proton efflux in these vesicles at all concentrations of sodium (2.5-50 mM) tested. Examination of the kinetic parameters for sodium-stimulated proton efflux in the presence and absence of 200 microM S-adenosyl-L-methionine revealed that the methyl donor increased the Vmax for this exchange mechanism (expressed in arbitrary fluorescence units) by approx. 36% but did not influence its Km for sodium. S-Adenosyl-L-homocysteine (2 mM) inhibited S-adenosyl-L-methionine-mediated stimulation of this exchange process. The results demonstrate that methylation of membrane phospholipids and/or proteins can modulate Na+-H+ exchange in rat colonic brush-border membrane vesicles.
D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D003106:Colon / Q000378:metabolism*; D005454:Fluorescence Polarization; D006859:Hydrogen / Q000378:metabolism*; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000378:metabolism*; D008560:Membrane Fluidity; D008563:Membrane Lipids / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D008745:Methylation; D008871:Microvilli / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism; D051381:Rats; D012436:S-Adenosylmethionine / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers
D002352:Carrier Proteins; D008563:Membrane Lipids; D008565:Membrane Proteins; D010743:Phospholipids; D017923:Sodium-Hydrogen Exchangers; D012436:S-Adenosylmethionine; D006859:Hydrogen; D012964:Sodium