Trp230, strategically located at the bottom of the active site, adopts different rotamer conformations depending on the presence of ligands (Fig. 4B and C). The equivalent in the GDPD from Thermus thermophofilus is Trp192 (PDB code: 1VD6). In the presence of PEG (PDB code: 3RLH) or glycerol (PDB code: 1VD6) molecules, Trp230(192) forms one of the walls of the active site pocket, freeing space for ligand binding. The presence of a sulfate
beta Interleukin 2 (44-56) in the active site of class I PLD (PDB code: 1XX1) induces another conformation of Trp230 by the formation of a
hydrogen bond between the NE1 nitrogen of Trp230 and the sulfate O1 atom. Contrastingly, in the ligand free form of class I PLD (PDB code: 2F9R), the Trp230 ring adopts a third conformation in which the torsion angle χ2 changes by ?90° in relation to the Trp230 conformation in presence of PEG or glycerol. These findings suggest that Trp230 motions might play a pivotal role in substrate binding in both Loxosceles venom PLDs and bacterial GDPDs.
