Involved in tumorigenesis and may function as a negative regulator of the p53/TP53 (PubMed:12879013). May play an essential role for mitochondrial structure and function, and thermogenesis of brown adipocytes (PubMed:34669999). May regulate phagocytosis and inflammatory responses to lipopolysaccharide in macrophages (By similarity). Interacts with BRI3BP. Highly expressed in brown adipose tissue (BAT). Up-regulated in adipose tissues upon cold exposure. Homozygous mice for Letmd1 gene are born at normal Mendelian ratios, with normal morphology, bodyweight and body composition at 2-months old (PubMed:34669999). Mice could not tolerate cold exposure without food (PubMed:34669999).