Irreversible inhibition of hepatic fatty acid salt uptake by photoaffinity labeling with 11, 11-azistearate.
In order to have a model compound for detection of proteins involved in transport and metabolism of long-chain fatty acid salts by photoaffinity labeling 11,11-azistearate and 11,11-azi[G-3H]stearate (specific radioactivity 2.78 TBq/mmol) were synthesized. The suitability of 11,11-azi[G-3H]stearate for photoaffinity labeling was demonstrated by incorporation into BSA (bovine serum albumin) and H-FABP (hepatic fatty acid salt-binding protein) of rat liver. Repeated photoaffinity labeling resulted in a clear decrease of the binding capacities of both proteins. Labeling of protein mixtures with 11,11-azi[G-3H]stearate showed that binding proteins for long-chain fatty acid salts interact specifically with this probe. Photoaffinity labeling of isolated hepatocytes using 300 microM 11,11-azistearate in the presence of 100 microM BSA resulted in the irreversible inhibition of the uptake of stearate and its analogue 2,2,3,3,18,18,18-heptafluorostearate nearly to the same extent of about 30%. Irreversible inhibition of the uptake of long-chain fatty acid salts by photoaffinity labeling did not alter the mediated transport of cholyltaurine and has no effect on the uptake of 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha-triol, a compound that crosses the hepatocyte membrane by simple diffusion. The irreversible inhibition of membrane transport by photoaffinity labeling demonstrates the existence of a specific transport system for the uptake of long-chain fatty acid salts into hepatocytes.
Schmider
W
W
Institut für Organische Chemie und Biochemie, Universität Freiburg, Germany.
Fahr
A
A
Voges
R
R
Gerok
W
W
Kurz
G
G
D000345:Affinity Labels / Q000494:pharmacology*; D000818:Animals; D001391:Azo Compounds / Q000494:pharmacology*; D001693:Biological Transport, Active / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids / Q000138:chemical synthesis / Q000737:chemistry / Q000493:pharmacokinetics*; D066298:In Vitro Techniques; D008099:Liver / Q000187:drug effects* / Q000378:metabolism*; D008297:Male; D018996:Myelin P2 Protein / Q000378:metabolism; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D010782:Photolysis; D011485:Protein Binding; D051381:Rats; D017208:Rats, Wistar; D012710:Serum Albumin, Bovine / Q000378:metabolism; D013229:Stearic Acids / Q000494:pharmacology*
C103296:11,11-azi-stearic acid; D000345:Affinity Labels; D001391:Azo Compounds; D002352:Carrier Proteins; C490174:Fabp7 protein, rat; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids; D018996:Myelin P2 Protein; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D013229:Stearic Acids; D012710:Serum Albumin, Bovine