InterPro domain: IPR002030

A variety of substrate carrier proteins that are involved in energy transfer are found in the inner mitochondrial membrane [ 1 , 2 , 3 , 4 , 5 ]. Such proteins include: ADP,ATP carrier protein (ADP/ATP translocase); 2-oxoglutarate/malate carrier protein; phosphate carrier protein; tricarboxylate transport protein (or citrate transport protein); Graves disease carrier protein; yeast mito- chondrial proteins MRS3 and MRS4; yeast mitochondrial FAD carrier protein; and many others.

The brown fat uncoupling protein (UCP) dissipates oxidative energy into heatby transporting protons from the cytosol into the mitochondrial matrix [ 6 ].UCP functions as a dimer, forming a proton channel that leads to uncouplingof oxidative phosphorylation by dissipation of the electrochemical potentialacross the inner membrane.

The protein has a tripartite structure, with 3 similar ~100 residue domains.The domains exhibit striking conservation of several residues, especiallyof glycine and proline, which may constitute structurally strategicpositions [ 7 ]. The protein is thought to contain 6 transmembrane helices[ 8 ]. These characteristics are shared by the ADP/ATP carrier protein, whichis a member of the mitochondrial carrier family.

1. Mechanism and evolution of the uncoupling protein of brown adipose tissue. Trends Biochem. Sci. 15, 108-12
2. Expansion of the mitochondrial carrier family. Res. Microbiol. 144, 671-2
3. Site-directed mutagenesis of the yeast mitochondrial ADP/ATP translocator. Six arginines and one lysine are essential. J. Mol. Biol. 230, 1159-70
4. Mitochondrial carrier proteins. FEBS Lett. 346, 48-54
5. PMP47, a peroxisomal homologue of mitochondrial solute carrier proteins. Trends Biochem. Sci. 18, 427-8
6. Human uncoupling protein gene: structure, comparison with rat gene, and assignment to the long arm of chromosome 4. J. Cell. Biochem. 43, 255-64
7. The uncoupling protein from brown fat mitochondria is related to the mitochondrial ADP/ATP carrier. Analysis of sequence homologies and of folding of the protein in the membrane. EMBO J. 4, 2369-76
8. The mitochondrial uncoupling protein gene. Correlation of exon structure to transmembrane domains. J. Biol. Chem. 263, 12274-7