Figure 9.

Sequence alignment of PFL-AE with other activating enzymes and selected radical SAM enzymes. This alignment focuses on the PFL-AE DTX₂₁MXD motif, and has been truncated to show only the region between beta2 to alpha4 for clarity. In the sequences that have been characterized structurally, beta strands are highlighted in yellow and alpha helices are highlighted in cyan. The residues of the PFL-AE DTX₂₁MXD motif are highlighted in pink and shown in bold text. Residues of this motif that are conserved in the other sequences are highlighted in pink, and conservative substitutions of residues in the motif are highlighted in maroon with bold white lettering. Note that at the positions corresponding to D104 and D129, acidic residues are highlighted in pink, and any other amino acid side chain that could act as a hard metal ligand is highlighted as a conservative substitution. The sequences aligned are E. coli pyruvate formate-lyase activating enzyme (UniProtKB ID P0A9N4), T. aromatica benzylsuccinate synthase activating enzyme (O87941), P. difficile 4-hydroxyphenylacetate decarboxylase activating enzyme (C9XIS7), C. butyricum glycerol dehydratase activator (Q8GEZ7), E. coli anaerobic ribonucleoside-triphosphate reductase-activating protein (P0A9N8), C. perfringens anaerobic sulfatase-maturating enzyme (Q0TTH1), E. coli oxygen-independent coproporphyrinogen III oxidase (P32131), E. coli biotin synthase (P12996), S. aureus molybdenum cofactor biosynthesis protein A (P65388), C. subterminale lysine 2,3-aminomutase (Q9XBQ8), C. hydrogenoformans HydG protein (Q3ABV3), T. maritima [FeFe]-Hydrogenase matures HydE (Q9X0Z6), B. circulans BtrN (Q8G907), E. coli ribosomal RNA large subunit methyltransferase N (P36979), and G. thermodenitrificans spore photoproduct lyase (A4IQU1).