Abstract

It has been estimated that a typical living cell is packed with between 2 and 4 million proteins per cubic micron. In nature the most common oligomeric state of the protein is a dimer, while the monomer is far less common. Many biologists surmise this is simply a consequence of sequestration and packing efficiency in a highly crowded environment. Chemists often argue that proteins are probably dimers for reasons of binding and catalytic cooperativity. Physicists are just plain happy to see another example of symmetry. Our studies have focused on a homodimeric bacterial enzyme, which exhibits no cooperativity whatsoever. Upon binding of the first substrate, the second substrate is excluded from the empty protomer and instead, the empty protomer facilitates key dynamic steps necessary for catalysis. I will discuss recent NMR experiments aimed at identifying functional states of this dynamic homodimer in addition to studies aimed at understanding substrate inhibition.