Size analysis of uncoupling protein and its precursor from brown adipose tissue of different species

The apparent size of the monomeric form of uncoupling protein from brown adipose tissue of several mammalian species was compared by sodium dodecyl sulfate - polyacrylamide gel electrophoresis. Including earlier results the apparent molecular mass of the protein from rat was about 32 000 daltons and varied about 1500-2000 daltons from the different sources with the size increasing in the order human less than rat less than or equal to mouse less than hamster less than or equal to rabbit. The size of newly synthesized uncoupling protein was also found to vary among species. However in the two cases examined, rat and rabbit, the precursor and its respective mature monomeric protein had the same apparent size as shown by coelectrophoresis.