Physiology, question allosterism

The existence of two distinct functions within the one membrane protein raises a number of interesting questions about transporter functions, such as what is the relative importance of the two functions Can they be allosterically regulated under physiological conditions or manipulated by pharmacological methods What is the structural basis for the dual functions In the next section, we shall attempt to address some of these issues and also to present some of the current understanding of the structural basis for these functional states. 

Next, I would like to raise the question whether any control mechanisms operate past the mevalonate stage. I am unaware of any experimental evidence to date for a physiologically significant regulation of the intermediate steps between mevalonic acid and cholesterol, either by repression, induction or allosterically. 

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