Mitochondrial uncoupling protein 2 is a protein that in humans is encoded by the UCP2 gene. [5]
Mitochondrial uncoupling proteins (UCP) are members of the larger family of mitochondrial anion carrier proteins (MACP). UCPs separate, or uncouple, oxidative phosphorylation from ATP synthesis by dissipating the mitochondrial membrane potential as heat, also referred to as the mitochondrial proton leak. UCPs facilitate the transfer of anions from the inner to the outer mitochondrial membrane and the return transfer of protons from the outer to the inner mitochondrial membrane. They also reduce the mitochondrial membrane potential in mammalian cells, which reduces production of reactive oxygen species (ROS).
In contrast to UCP1 and UCP3, which are primarily expressed in adipose and smooth muscle, UCP2 is expressed on many different tissues [6] including the kidney, liver, GI tract, brain, and skeletal muscle.
The exact mechanisms of anion transfer by UCPs are not known. [7] UCPs contain the three homologous protein domains of MACPs. Although it was originally thought to play a role in non-shivering thermogenesis, obesity, diabetes and atherosclerosis, it now appears that the main function of UCP2 is the control of mitochondria-derived reactive oxygen species. [8]
Chromosomal order is 5'-UCP3-UCP2-3'. [9]
Thermogenin is a mitochondrial carrier protein found in brown adipose tissue (BAT). It is used to generate heat by non-shivering thermogenesis, and makes a quantitatively important contribution to countering heat loss in babies which would otherwise occur due to their high surface area-volume ratio.
An uncoupling protein (UCP) is a mitochondrial inner membrane protein that is a regulated proton channel or transporter. An uncoupling protein is thus capable of dissipating the proton gradient generated by NADH-powered pumping of protons from the mitochondrial matrix to the mitochondrial intermembrane space. The energy lost in dissipating the proton gradient via UCPs is not used to do biochemical work. Instead, heat is generated. This is what links UCP to thermogenesis. However, not every type of UCPs are related to thermogenesis. Although UCP2 and UCP3 are closely related to UCP1, UCP2 and UCP3 do not affect thermoregulatory abilities of vertebrates. UCPs are positioned in the same membrane as the ATP synthase, which is also a proton channel. The two proteins thus work in parallel with one generating heat and the other generating ATP from ADP and inorganic phosphate, the last step in oxidative phosphorylation. Mitochondria respiration is coupled to ATP synthesis, but is regulated by UCPs. UCPs belong to the mitochondrial carrier (SLC25) family.
Mitochondrial uncoupling protein 3 is a protein that in humans is encoded by the UCP3 gene. The gene is located in chromosome (11q13.4) with an exon count of 7 and is expressed on the inner mitochondrial membrane. Uncoupling proteins transfer anions from the inner mitochondrial membrane to the outer mitochondrial membrane, thereby separating oxidative phosphorylation from synthesis of ATP, and dissipating energy stored in the mitochondrial membrane potential as heat. Uncoupling proteins also reduce generation of reactive oxygen species.
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Daniel Ricquier, is a French biochemist known for his work in mitochondria and hereditary metabolic diseases. Ricquier has been a member of the French Academy of Sciences since 2002, and a professor of biochemistry and Molecular Biology at the Faculty of Medicine of the University of Paris Descartes since 2003.