Uncoupling protein 1: a short-circuit in the chemiosmotic process.

One of the significant naturally occurring short-circuits in the chemiosmotic process is manifest through the activity of uncoupling protein 1, most notably present in the inner membrane of mitochondria in brown adipose tissue. Much has been learnt about the mechanism of action of uncoupling protein 1 since its discovery in the 1970's, yet many areas of controversy surround (i) the mechanism of its action, (ii) novel regulators of its activity, and (iii) the tissue specificity of its expression. In this mini-review, areas of controversy are highlighted from the aforementioned categories using selected key experiments to demonstrate the arguments.