Figure 2
From: Structure, function, and inhibition of drug reactivating human gut microbial β-glucuronidases
Crystal structures of L1 FpGUS, LrGUS, and RgGUS enzymes. (a) Monomeric tertiary structures of FpGUS (cyan), LrGUS (magenta), and RgGUS (dark pink). (b) Tetrameric quaternary structures of FpGUS, LrGUS, and RgGUS with a single monomer highlighted and identical monomers in its muted colour. (c) Active sites of FpGUS, LrGUS, and RgGUS. An arrow points to the Loop 1 structure in RgGUS. In FpGUS and LrGUS, the loop is disordered. A magnesium ion was built into the electron density within the FpGUS active site. Given the crystallisation conditions (which contained magnesium formate), relatively solvent exposed active site observed in the structure, and the absence of unique coordinating residues, the ion is most likely an artefact from crystallization and is not expected to play a functional role in catalysis. Glycerol molecules are highlighted in yellow. Catalytic glutamates are boxed.
