A plasmid region encoding the active fragment and the inhibitor protein of colicin E3--CA38

Thermogenin is the purine-nucleotide binding polypeptide in brown adipose tissue mitochondria (M_r 32 000) which confers upon these mitochondria the ability to produce heat. An enzyme-linked immunosorbent assay (ELISA) has been developed to demonstrate and quantitate the occurrence of thermogenin antigen in small amounts of tissue, and thus to characterize different depots of fat tissue as white or brown. The extreme sensitivity of the method allows determination of thermogenin in samples equivalent to <1 mg tissue. The results indicate that thermogenin seems to be exclusively localised in brown fat mitochondria (as compared to white fat, liver or heart muscle mitochondria), and thermogenin antigen could only be found in brown adipocytes (as compared to white adipocytes). Thus, brown and white adipose tissue are probably ontogenetically different