NirJ is involved in the transformation of precorrin-2 into heme d1, although its precise role in the process has not been established. The purified protein was found to contain a 4Fe-4S centre, in line with the prediction that it belongs to the radical SAM class of enzymes. This was further confirmed by binding of S-adenosyl-l-methionine (SAM) to dithionite-reduced NirJ, which resulted in a decrease in the signal intensity and in a shift to higher field of the [4Fe-4S]1+ EPR signal. Significantly, though, this approach also led to the appearance of a small but reproducible organic radical signal that was associated with about 2% of the NirJ molecules and was affected by the incorporation of SAM deuterated at the 5' adenosyl group. © 2010 Federation of European Biochemical Societies.
Brindley, A. A., Zajicek, R., Warren, M. J., Ferguson, S. J., & Rigby, S. E. J. (2010). NirJ, a radical SAM family member of the d1 heme biogenesis cluster. FEBS Letters, 584(11), 2461–2466. https://doi.org/10.1016/j.febslet.2010.04.053