TtcA enzyme is not directly involved in catalysis but had a structural role that affects the folding of the enzyme. In vitro enzyme assays found only TtcA containing [4Fe-4S] cluster was active. So, TtcA is unique tRNA-thiolating enzyme using an iron-sulfur cluster for catalyzing a thiolation of tRNA by three cysteine residues.
In my senior project, we found the TtcA in P. aeruginosa too that is about tRNA modification and iron-sulfer cluster [4Fe-4S] is about oxygen sensitive. Then. I am studying the physiological function of P. aeruginosa ttcA under stress conditions by using site directed mutagenesis. To study which cysteine residues in P. aeruginosa that are importance for ttcA gene.