RquA, a protein expressed from the rquA gene in bacteria and some protists, is required for the conversion of ubiquinone (UQ) to rhodoquinone (RQ). RQ is an essential electron carrier used in anaerobic metabolism. Sequence analysis of RquA has revealed an S‐adenosyl methionine (SAM) binding domain. It has been hypothesized that SAM acts as the amino source or a catalyst for the conversion of UQ to RQ. The aim of this study was to determine the requirements for RquA function. Assays were performed in vitro under various conditions with refolded RquA and a synthetic UQ3 substrate. The resulting amounts of RQ3 produced were quantified using LC‐MS. In the absence of SAM, assays have not produced RQ3, suggesting that SAM is required for RquA function. The requirement of zinc (II) has also been demonstrated, with assays performed in its absence failing to yield RQ3. Increasing the concentration of either SAM or RquA present in the assay resulted in a corresponding increase in RQ3. These results show that SAM and Zn2+ are required for the function of RquA. Kinetic assays to further characterize RquA are currently underway.
Lydia R. Chambers, Alexander K. Godfrey, Melina Monlux
The FASEB Journal