title: Chemical modification of the brown-fat-mitochondrial uncoupling protein with tetranitromethane and N-ethylmaleimide. A cysteine residue is implicated in the nucleotide regulation of anion permeability.
abstract: Treatment of brown adipose tissue mitochondria with tetranitromethane or N-ethylmaleimide decreases the affinity with which inhibitory nucleotide GDP binds to the tissue-specific uncoupling protein. Both reagents modify cysteine residues which are 'accessible' and 'buried' to 5,5'-dithio-bis(2-nitrobenzoic acid) (Nbs2). Modification of the single Nbs2-accessible residue correlates with the loss of high-affinity binding sites for GDP. Tetranitromethane does not affect the Cl- or H+ permeability of the protein in the absence of nucleotide, while N-ethylmaleimide increases both by 70-80%. Bound GDP is a less effective inhibitor of Cl- permeability after N-ethylmaleimide or tetranitromethane treatment, but retains much of the ability to inhibit H+ permeation.
mesh_terms: D002001:Adipose Tissue, Brown / Q000378:metabolism*; D000818:Animals; D002352:Carrier Proteins; D002712:Chlorides / Q000378:metabolism; D006224:Cricetinae; D003545:Cysteine / Q000378:metabolism; D005033:Ethylmaleimide / Q000494:pharmacology; D006153:Guanosine Diphosphate / Q000378:metabolism; D007473:Ion Channels; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D008647:Mesocricetus; D008697:Methane / Q000031:analogs & derivatives; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins; D010539:Permeability; D011485:Protein Binding / Q000187:drug effects; D011522:Protons; D013774:Tetranitromethane / Q000494:pharmacology; D000071256:Uncoupling Protein 1
chemical_list: D002352:Carrier Proteins; D002712:Chlorides; D007473:Ion Channels; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D011522:Protons; D000071256:Uncoupling Protein 1; D006153:Guanosine Diphosphate; D013774:Tetranitromethane; D003545:Cysteine; D005033:Ethylmaleimide; D008697:Methane