Uncoupling proteins

The third time constraint depends on whether the product can be extracted from seeds or fruits. This uncouples protein expression and purification. Large batches of seeds containing the recombinant protein can be produced and stored at low costs. Provided the protein remains stable in the stored seeds, purification can be carried out on demand or shifted according to free capacities. The advantage of one large harvest, with seeds mixed to uniformity, is that this allows production on demand. In contrast, mammalian cell culture is prone to minor batch-to-batch variations in... 

Casteilla et al. [26] suggested that mitochondrial superoxide production is modulated by uncoupling proteins. It has also been proposed [27] that the production of superoxide by... 

Unconsolidated ocean deposits, 17 686-691 Uncontrolled variables, 3 388-389 Uncouplers, 14 349 Uncoupling proteins... 

Because the rate of the ETC increases, with no ATP synthesis, energy is released as heat. Important uncouplers include 2,4-dinitrophenol (2,4-DNP) and aspirin (and other salicylates). Brown adipose tissue contains a natural uncoupling protein (UCP, formerly called thernio-genin), which allows energy loss as heat to maintain a basal temperature around the kidneys, neck, breastplate, and scapulae in newborns. 

Stimulation of the sympathetic nervous system releases noradrenaline which stimulates mobilisation of fatty acids in adipose tissue. The latter stimulate the activity of the uncoupling protein. 

There are several properties of the uncoupling protein that are consistent with this hypothesis. 

In summary, the fuel that is oxidised to provide the energy is fatty acids but the energy is converted to heat, via the increased activity of the uncoupling protein. The increased activity of the uncoupling protein is due to the increased concentration of fatty acids (Figure 9.29). 

In order to provide heat when it is required to maintain or increase body temperature, a mechanism must exist for the regulation of the activity of this uncoupling protein. The mechanism has been established by following the principles described in Chapter 3. The properties of the uncoupling protein are studied using mitochondria isolated from brown adipose tissue in vitro (as described in Appendix 9.9). 

The properties are as follows, (i) The activity of the protein (i.e. the inward transport of protons) is inhibited by ATP. (ii) The activity of the protein is increased by the presence of long-chain fatty acids, since they relieve the ATP inhibition, (iii) When mitochondria, isolated from brown adipose tissue, are incubated in the presence of fatty acids, there is a sharp increase in the rates of electron transfer, substrate utilisation and oxygen consumption, whereas the rate of ATP generation remains low. These studies indicate that the rate of proton transport, by the uncoupling protein, depends on the balance between the concentrations of ATP and fatty acids, (iv) In adipocytes isolated from brown adipose tissue, the rate of oxygen consumption (i.e. electron transfer) is increased in the presence of catecholamines. 

Figure 9.29 Control of heat production in brown adipose tissue. Catecholamines increase cyclic AMP concentrab on which stimulates triacylglycerol lipase which increases the long-chain fatty acid level, which increases the fluxes through P-oxidation and the Krebs cycle, and the activity of the uncoupling protein. Uncoupling decreases the ATP concentration which further increases the activity of the uncoupling.

Naudi, A., Caro, P., Jove, M., Gomez, J., Boada, J., Ayala, V., Portero-Otin, M., Barja, G., and Pamplona, R. (2007). Methionine restriction decreases endogenous oxidative damage and increases mitochondrial biogenesis and uncoupling protein 4 in rat brain. Rejuvenation Res. 10,473M84. 

Uncoupling protein expression. Oil, administered to female Wistar rats fed ad libitum a high-fat diet with coconut oil for 7 weeks, promoted an increase in body fat content, body weight, and uncoupling protein levels. At the completion of experiment 1, oil was administered to high-fat diet rats for 3 weeks. Adipose depots were strongly reduced in the rats fed the high fat... 

Y. Masuda, S. Haramizu, K. Oki, K. Ohnuki, T. Watanabe, S. Yazawa, T. Kawada, S. Hashzume and T. Fushiki, Upregulation of uncoupling proteins by oral administration of capsiate, a nonpungent capsaicin analog. /. Appl. Physiol, 2003, 95, 2408-2415. 

B. Faraut, B. Giannesini, V. Matarazzo, Y. Le Fur, G. Rougon, P. J. Cozzone and D. Behdahan, Capsiate administration results in an uncoupling protein-3 downregula-tion, an enhanced muscle oxidative capacity and a decreased abdominal fat content in vivo. Int. J. Obes. (Lond), 2009, 339,1348-1355. 

FIGURE 3.9 Western blotting analysis of uncoupling protein 1 (UCP1) in epididymal WAT and relative expression level of UCP1 protein compared to p-actin (Okada etal., 2011). Columns with different superscript letters are significantly different (p<0.05). 

Thermogenin (uncoupler protein), a proton pore of 19-30, 23-22 mitochondrial inner membrane... 

FIGURE 19-30 Heat generation by uncoupled mitochondria. The uncoupling protein (thermogenin) of brown fat mitochondria, by providing an alternative route for protons to reenter the mitochondrial matrix, causes the energy conserved by proton pumping to be dissipated as heat. 

The mitochondria of brown fat are like those of other mammalian cells in all respects, except that they have a unique protein in their inner membrane. Thermogenin, also called the uncoupling protein (Table 19-4), provides a path for protons to return to the matrix without passing through the F0Fx complex (Fig. 19-30). 

Klingenberg, M. Huang, S.-G. (1999) Structure and function of the uncoupling protein from brown adipose tissue. Biochim. Biophys. Acta 1415, 271-296. 

Freake, H.C. (1998) Uncoupling proteins beyond brown adipose tissue. Nutr. Rev. 56, 185-189. 

Review of the structure, function, and role of uncoupling proteins. 

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