Evolution allosteric proteins

Doi, N., and Yanagawa, H. (1999). Design of generic biosensors based on green fluorescent proteins with allosteric sites by directed evolution. FEBS Lett., 453, 305-307. 

The hemoglobin family of macromolecules exhibits virtually all the important features of protein structure, function, and evolution, principles of protein folding, subunit movement and allosteric control in regulating activity, effects of point mutations on molecular behavior, and gene structure and genetic control. 

Regulation can also occur at the protein level, such as allosteric regulation that prevents the wasteful conversion of costly metabolites. Such regulation is expected to be, and in many cases is, product-controlled. However, in many cases, the substrate also comprises of an allosteric regulator of its own enzyme - in other words, in the absence of its substrate, the enzyme active site becomes inactive. Preventing the active sites from promiscuously reacting with other, undesirable substrates could be one of the driving forces for the evolution of such mechanism. 

Under normal conditions the inductor is a diffusible substance or group of substances, metabolic products of the neighboring tissue. The closer the contact, the higher the concentration of these products. For this reason the reaction of the receptor systems has not developed very narrow specificity in the course of evolution. A reaction has developed to a signal, which could be an individual compound. However, this does not mean that other compounds cannot act as such signals. Under normal conditions other compounds simply are not present, and the receptor systems have not therefore developed very narrow specificity of reaction such as occurs during the allosteric interaction of specific proteins in the phenomena of substrate induction in bacteria (see Chapter 3). 

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