Which is a natural uncoupler?

Uncouplers of Oxidative Phosphorylation: Uncouplers will allow oxidation to proceed, but the energy instead of being trapped by phosphorylation Fig. 19.18. Impoant mitochondrial membrane transpoers. 1 = PYT (pyruvate transpoer); 2 = TCT (tricarboxylate transpoer); 3 = ANT (adenine nucleotide transpoer) is dissipated as heat. This is achieved by removal of the proton gradient. (Table 19.5; Fig. 19.17). The uncoupling of oxidative phosphorylation is useful biologically. In hibernating animals and in newborn human infants, the liberation of heat energy is required to maintain body temperature. In Brown adipose tissue, thermogenesis is achieved by this process. Thermogenin, a protein present in the inner mitochondrial membrane of adipocytes, provides an alternate pathway for protons. It is one of the uncoupling proteins (UCP). Thyroxine is also known to act as a physiological uncoupler.Ref: DM Vasudevan Textbook of Medical Biochemistry, 6th edition, page no: 234