title: [125I]Iodonaphtylazide labeling selectively a cysteine residue in the F0 of the ATP-synthase from E. coli is unsuitable for topographic studies of membrane proteins.
abstract: The ATP synthase from E. coli was reacted with the hydrophobic photolabel [125I]iodonaphtylazide. Subunit b in the F0-part was selectively labelled. Label was traced back to the single cysteine21 in subunit b. Thus the reactive intermediate of INA generated by photolysis had a high preference for nucleophiles. Due to this high selectivity the detection of membrane spanning peptide segments by labelling with INA is not reliable.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D001386:Azides; D003488:Cyanogen Bromide; D003545:Cysteine; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D007457:Iodine Radioisotopes; D008565:Membrane Proteins / Q000378:metabolism*; D010446:Peptide Fragments / Q000032:analysis; D010957:Plasmids; D011485:Protein Binding; D006180:Proton-Translocating ATPases
chemical_list: D001386:Azides; D007457:Iodine Radioisotopes; D008565:Membrane Proteins; D010446:Peptide Fragments; C015298:iodonaphthylazide; D000251:Adenosine Triphosphatases; D006180:Proton-Translocating ATPases; D003545:Cysteine; D003488:Cyanogen Bromide