Correction to “Identification and Characterization of the Biosynthesis of the Hybrid NRPS-NIS Siderophore Nocardichelin”

In the original manuscript, six mutants of the NcdE-ATx domain were constructed and tested for the ability to produce N-hydroxy-N-succinylcadaverine in the coupled assay, which was monitored by LC-MS. In follow-up experiments since publication, a 1.4 Å crystal structure was solved for the mutant protein thought to be the H1240A mutant. The electron density unequivocally showed that this protein was not the H1240A but rather was the Y1214A mutant. As the same protein sample was used in the biochemical activity assay and the crystallization experiment, the original data reported in Figure 8 for the H1240A mutant was in fact a repeat of the Y1216A mutant.Relative activity among NcdE-ATx mutants compared to the wildtype. Reactions were performed with NcdE-ATx enzymes, quenched, and separated by LC-MS (Supporting Figure 10). The area of peaks from EICs were used to monitor HSC biosynthesis. For each reaction, a background reaction was run with no NcdE-ATx, showing a small spontaneous peak that was subtracted from each reaction. The ratios of corrected peak areas for mutant to wild-type of three independent reactions were combined and presented here (*** p < 0.01, **** p < 0.0001). We identified the correct clone from our cellular stocks, resequenced the mutant plasmid, and purified the H1240A mutant for biochemical analysis. The assay was performed as described in the original manuscript, except N-hydroxycadaverine was produced directly from cadaverine with NcdJ and not from the combined action of decarboxylase NcdI and hydroxylase NcdJ on lysine, as performed in the original experiment. The LC-MS assay illustrated that the histidine mutant was in fact severely compromised.