Abstract
Mycofactocin is a
putative redox cofactor and is classified as
a ribosomally synthesized and post-translationally modified peptide
(RiPP). Some RiPP natural products, including mycofactocin, rely on
a radical S-adenosylmethionine (RS, SAM) protein
to modify the precursor peptide. Mycofactocin maturase, MftC, is a
unique RS protein that catalyzes the oxidative decarboxylation and
C–C bond formation on the precursor peptide MftA. However,
the number, chemical nature, and catalytic roles for the MftC [Fe–S]
clusters remain unknown. Here, we report that MftC binds a RS [4Fe–4S]
cluster and two auxiliary [4Fe–4S] clusters that are required
for MftA modification. Furthermore, electron paramagnetic resonance
spectra of MftC suggest that SAM and MftA affect the environments
of the RS and Aux I cluster, whereas the Aux II cluster is unaffected
by the substrates. Lastly, reduction potential assignments of individual
[4Fe–4S] clusters by protein film voltammetry show that their
potentials are within 100 mV of each other.