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. 2016 Jul 3;138(29):9277–9293. doi: 10.1021/jacs.6b05134

Figure 3.

Figure 3

Proposed second magnesium binding site. (A) The magnesium binding sites in EntC (PDB ID 3HWO). The catalytic magnesium is labeled 1, and the additional site is labeled 2. Isochorismate is shown in cyan sticks. The general base (K147) and general acid (E197) are shown in yellow. The residues of the turn that bind the secondary magnesium are shown in green. This turn connects an α-helix to the β-strand that is initiated at the general base. (B) Sequence alignment for the loop highlighted in (A), comparing PchA, EntC, and Irp9. It should be noted that the residue side chain (colored) that chelates the second magnesium in the 3HWO structure is not conserved among the three proteins. The lysine in bold is the general base residue. (C) Steady-state magnesium dependence for three forms of Irp9: WT (circles), V192D (squares), and V192G (triangles). (D) Steady-state magnesium dependence for three forms of EntC: WT (circles), D146G (squares), and D146V (triangles). (E) Steady-state magnesium dependence for three forms of PchA: WT (circles), G220D (squares), and G220V (triangles).