Fig. 2: 4-Nitro-L-2-aminobutyric acid as a chain terminator of poly-γ-glutamylation in folates and F420.
A poly-γ-glutamate tail is shown with variable L-glutamate numbers and terminated by a non-reactive nitro functional group. Calculated masses of nitro-terminated folate and F420 molecules are provided for comparison to experimental results – the central number indicates the total residue count in the tail including the chain terminator residue. The masses take into account functional group protonation within the mass spectrometer operating in positive ion mode and are provided to 4 decimal places to match the precision of the high-resolution LC-MS experiment. The table of data provides the identity and experimentally measured masses of substrate, predominant polyglutamylated product, and nitro-terminated product. Enzymes systems investigated are human FPGS (hFPGS), Mycobacterium tuberculosis FPGS (Mtb-FPGS), Archaeoglobus fulgidus CofE (Af-CofE), and Mycobacterium tuberculosis FbiB (Mtb-FbiB).
