Binds to an ERR-alpha response element (ERRE) containing a single consensus half-site, 5'-TNAAGGTCA-3'. Can bind to the medium-chain acyl coenzyme A dehydrogenase (MCAD) response element NRRE-1 and may act as an important regulator of MCAD promoter. Binds to the C1 region of the lactoferrin gene promoter. Requires dimerization and the coactivator, PGC-1A, for full activity. The ERRalpha/PGC1alpha complex is a regulator of energy metabolism. Induces the expression of PERM1 in the skeletal muscle (By similarity). Binds DNA as a monomer or a homodimer. Interacts (via the AF2 domain) with coactivator PPARGC1A (via the L3 motif); the interaction greatly enhances transcriptional activity of genes involved in energy metabolism. Interacts with PIAS4; the interaction enhances sumoylation (By similarity). Interacts with MAPK15; promotes re-localization of ESRRA to the cytoplasm through a XPO1-dependent mechanism then inhibits ESRRA transcriptional activity (PubMed:21190936). Co-localizes to the cytoplasm only in presence of MAPK15. Most highly expressed in kidney, heart, and brown adipocytes. Also found in uterus, cervix and vagina. Expressed in an organ specific manner through mid- to late embryonic development with persistent high-level expression in brown adipose tissue and intestinal mucosa. Activated by diethylstilbestrol (DES) and estradiol in the uterus. Phosphorylation on Ser-19 enhances sumoylation on Lys-14 increasing repression of transcriptional activity. Sumoylated with SUMO2. Main site is Lys-14 which is enhanced by phosphorylation on Ser-19, cofactor activation, and by interaction with PIAS4. Sumoylation enhances repression of transcriptional activity, but has no effect on subcellular location nor on DNA binding (By similarity). Reversibly acetylated. Acetylation by PCAF/KAT2 at Lys-129, Lys-138, Lys-160 and Lys-162 and PCAF/KAT2 decreases transcriptional activity probably by inhibiting DNA-binding activity; deacetylation involves SIRT1 and HDAC8 and increases DNA-binding (By similarity). No visible phenotype; mice are viable, fertile and display no gross anatomical alterations, with the exception of reduced body weight and peripheral fat deposits. Mice are resistant to a high-fat diet-induced obesity. Cardiomyocyte-specific double konckout for ESRRA and ESRRG are slower at gaining weight, smaller and shorter from 5 to 7 days of age compared to controls. They show decreased absolute weight of most internal organs except the heart. They have about 70% decreased plasma IGF1 levels but normal plasma growth hormone levels. At 14-15 days, mutants develop lethal dilated cardiomyopathy and heart failure (PubMed:28572090). Belongs to the nuclear hormone receptor family. NR3 subfamily.