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. 2019 Aug 15;294(37):13833–13849. doi: 10.1074/jbc.RA119.009910

Figure 6.

Figure 6.

Ega3 binds galactosamine using a flexible loop to create a substrate-binding tunnel. A, cartoon representation of the Ega3–GalN complex with transparent surface representation. B, alignment of apo-Ega3 (cyan) and Ega3–GalN (dark teal) showing the movement of the β3-insertion containing Glu-133, Trp-154, and Glu-157. C, galactosamine-binding site with the |Fo − Fc| omit map contoured at 3.0 σ. Residues that interact with galactosamine are in orange, and the putative catalytic acidic residues are in teal. D, comparison of the flexible loop contained in the β3-insertion of Ega3 (teal), Ega3–GalN (dark teal), PelAh (yellow, PDB 5TCB), and TM1410 (gray, PDB 2AAM). The unknown ligand in TM1410 is in red. E, sequence alignment of the β3-insertion of Ega3 orthologues, and TM1410 and PelAh based on the structural alignment. Residues in β-strands are in blue, and helices (310 and α) in yellow are shown in cartoon representation of the Ega3 2° structure above. Residues that bind galactosamine are shown in red. Sequence identity was calculated by ClustalOmega for Ega3 proteins, whereas TM1410, PelAh, and Sph3 sequence identity was determined through the structural alignments in Coot.