Abnormal DNA Binding by Metal Reconstituted CooA

This work is part of a larger project whose overarching goal is to learn how the binding of a small molecule, carbon monoxide, to a large protein causes the shape of that protein to dramatically change. The protein in question, called CooA, is found in a bacterial species where it serves as a carbon monoxide sensor. When carbon monoxide binds to CooA, the dramatic shape change causes CooA to bind to the bacterium’s DNA. This DNA binding enables the bacterium to make proteins that the cell then uses to consume the carbon monoxide as a food. The focus of the work reported here is to study a newly-discovered form of CooA where the specific carbon monoxide binding site, a heme-bound iron 3+ ion, has been removed and then readded (reconstituted). This reconstituted CooA shows activity without the presence of carbon monoxide. This is unusual because it is generally accepted that reduction of the iron and carbon monoxide together are required to activate DNA binding. To further test this behavior, other metals than iron were reconstituted and showed similar effects but provided a possible molecular explanation that accounted for carbon monoxide-independent DNA binding