The function of Ensembl gene identifier ENSG00000175564 (UCP3, uncoupling protein 3) is as follows. Putative transmembrane transporter that plays a role in mitochondrial metabolism via an as yet unclear mechanism (PubMed:21775425, PubMed:36114012). Originally, this mitochondrial protein was thought to act as a proton transmembrane transporter from the mitochondrial intermembrane space into the matrix, causing proton leaks through the inner mitochondrial membrane, thereby uncoupling mitochondrial membrane potential generation from ATP synthesis (PubMed:11171965, PubMed:12670931, PubMed:12734183, PubMed:9305858). However, this function is controversial and uncoupling may not be the function, or at least not the main function, but rather a consequence of more conventional metabolite transporter activity (PubMed:11707458). {ECO:0000269|PubMed:11171965, ECO:0000269|PubMed:11707458, ECO:0000269|PubMed:12670931, ECO:0000269|PubMed:12734183, ECO:0000269|PubMed:21775425, ECO:0000269|PubMed:36114012, ECO:0000269|PubMed:9305858}.