Extended Data Figure 7: HPLC-MS analysis of P450-catalysed peptide monocyclization.
From: X-domain of peptide synthetases recruits oxygenases crucial for glycopeptide biosynthesis
a–d, Representative HPLC-MS chromatograms of in vitro OxyBtei (a), StaH (b), OxyBvan (c), CepF (d) turnover reactions with heptapeptide Tei7(Hpg3,7) or Van7(Hpg7) bound to GB1–PCP7–X (left) and GB1–PCP7 (right). Ions corresponding to the singly charged, linear (hydrolysed m/z 1,088, methylhydrazide m/z 1,116) and crosslinked monocyclic (hydrolysed m/z 1,086, methylhydrazide m/z 1,114 ) teicoplanin-like peptide and the linear (hydrolysed m/z 1,017.5, methylhydrazide m/z 1,045.5 ) and crosslinked monocyclic (hydrolysed m/z 1,015.5, methylhydrazide m/z 1,043.5 ) vancomycin-like peptide recorded using single-ion monitoring (SIM) in negative mode. Major peaks for each mass represent diastereomers due to racemization of the C-terminal Hpg residue and two regioisomers derived from methylhydrazine cleavage; smaller peaks can be caused by overlapping mass signal detection with ions from lower molecular weight species; additionally, racemization of such crosslinked products has also been previously observed39.
