Figure 3
From: Opportunistic complexes of E. coli L-asparaginases with citrate anions
Mimicry of L-aspartate anions by citrate. A molecule of L-Asp is shown in a stick representation, in the conformation found for the complex with EcAII (PDB ID 3eca, monomer A). The overlaid citrate anions, drawn in line representation, are shown in three conformations, in which the α-carboxyl groups of L-Asp and citrate are aligned. Non-H atoms of citrate are labeled according to a convention used in crystal structures. Each of the three carboxylate groups (in citrate anion) is uniquely labeled, as α, β1, or β2 (panels a–c). While it appears that conformations of citrate shown in panels a and b fit the L-Asp best, mimicries depicted in panels b and c were observed in the structures described in this study (b in the case of re-refined entry 2him, new PDB ID 6nxc; c in the case of EcAIIwt-apo7, PDB ID 6nxb). Panel d illustrates protonation states of citrate at different pH values; it is generated based on data by Rao et al.35.
