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Figure 5
Binding modes of various ligands. The active sites of the sulfate-bound structure (a), malonate (MLA)-bound S128A mutant structure (b), PMSF-bound structure (c) and S128A mutant structure (d) are shown. The overall color scheme of PsEst3 is the same as that in Fig. 1[link](a). The 2Fo − Fc map of sulfate and malonate (blue) and the Fo − Fc map of unidentified ligands (green) are contoured at the 2σ level except for in the PMSF complex (1.5σ level). The hydrogen bonds between ligands and PsEst3 are represented as black dotted lines. The transition-state analog (diethyl phosphonate)-bound structure of an extracellular triglyceride lipase (PDB entry 4tgl) and the PMSF-bound structure of EstE5 (PDB entry 3h17) are superposed on PsEst3, and the diethyl phosphonate in PDB entry 4tgl and the PMSF in PDB entry 3h17 are represented as transparent stick models in (a) and (c), respectively. (e) Inhibition activity by malate (salt form), maleic acid, malonate and PMSF. The respective ligand was added in the concentration range 0.6–2.4 mM. (f) The pNP-ester (C2, C4, C6 and C8) hydrolysis activity measured with various Arg44 variants (R44K, R44G, R44F, R44S and R44D). (g) Relative activities of fluorescein derivatives (C4, C8 and C12) measured with various Arg44 variants.

IUCrJ
Volume 10| Part 2| March 2023| Pages 220-232
ISSN: 2052-2525
https://doi.org/10.1107/S2052252523001562