Structure of a complex of the potent and specific inhibitor BW284C51 withTorpedo californicaacetylcholinesterase

Abstract

The X-ray crystal structure of Torpedo californica acetylcholinesterase (TcAChE) complexed with BW284C51 {CO[ÐCH 2 CH 2 ÐpC 6 H 4 ÐN(CH 3 ) 2 (CH 2 ÐCH CH 2 )] 2 } is described and compared with the complexes of two other active-site gorge-spanning inhibitors, decamethonium and E2020. The inhibitor was soaked into TcAChE crystals in the trigonal space group P3 1 21, yielding a complex which diffracted to 2.85 A Ê resolution. The structure was re®ned to an R factor of 19.0% and an R free of 23.4%; the ®nal model contains the protein, inhibitor, 132 water molecules and three carbohydrate moieties. BW284C51 binds similarly to decamethonium and E2020, with its two phenyl and quaternary amino end-groups complexed to Trp84 in the catalytic site and to Trp279 in the peripheral binding site, and its central carbonyl group hydrogen bonded very weakly to Tyr121. Possible reasons for decamethonium's weaker binding are considered. The relative strength of binding of bisquaternary inhibitors to acetylcholinesterase and the effect of several mutations of the enzyme are discussed in the context of the respective X-ray structures of their complexes with the enzyme.

Comparative studies of acetylcholinesterase purified from three field populations of Liposcelis entomophila (enderlein) (psocoptera: liposcelididae)

“…However, BW284C51 did not exhibit inhibition difference between the purified AChEs from GH and WH populations. The current result is consistent with one previous report about Bactrocera dorsalis (Hsu et al, 2008), where one possible explanation was given for the fact that BW284C51 expressed weak effects on alteration of the interactions between the I214V and W121 sites of ace in B. dorsalis (Felder et al, 2002, Hsu et al, 2008. Though our results cannot give the comparisons of hydrolyzing ATChI and BTC, such good inhibitor specificities of the purified enzyme from the three populations also can indicate that the purified enzyme was a ''true'' AChE (Gao and Zhu, 2001;Ma et al, 2004).…”

“…Based on k i values, results showed that purified AChE was highly sensitive to inhibition by eserine (a general inhibitor for both AChE and butyrylcholinesterase or BChE) and BW284C51 (a relatively specific inhibitor of AChE). Felder et al (2002) found that BW284C51 compound is considered to be a very specific inhibitor of Torpedo californica AChE by comparing the X-ray structure of a complex of the BW284C51 with TcAChE. However, BW284C51 did not exhibit inhibition difference between the purified AChEs from GH and WH populations.…”

Substrate and Product Trafficking through the Active Center Gorge of Acetylcholinesterase Analyzed by Crystallography and Equilibrium Binding

“…5). These two compounds have the capacity to occupy both the active center gorge and the PAS, as shown for decamethonium or BW28C51 bound to crystalline TcAChE (34,41), although decidium may preferably occupy the PAS, as seen in the crystalline mAChE complex (19).…”

“…Initial manual docking of an ACh molecule into the Torpedo californica (TcAChE) structure (4) was followed by structures of AChE complexes with competitive, reversible inhibitors (34 -38), covalent organophosphate or carbamate inhibitors (39), bifunctional inhibitors (20,32,34,40,41), PAS inhibitors (5,18,19), and the substrate analogue, trimethylammoniotrifluoroacetophenone (TMTFA) (42). The latter provides a close structural mimic of the substrateAChE tetrahedral transition state.…”

Crystal Structure of Snake Venom Acetylcholinesterase in Complex with Inhibitory Antibody Fragment Fab410 Bound at the Peripheral Site

“…Finally, this predicted mode of Fab410 binding at the EeAChE PAS is also consistent with its competition with the large peptidic inhibitor Fas2 but absence of competition with the small organic inhibitors propidium, decamethonium, BW284C51, and the substrate acetylcholine when in excess (31). In fact, structural comparison of the crystalline Fab410-BfAChE and modeled Fab410-EeAChE complexes with crystalline mAChE or TcAChE complexes with acetylcholine (8,9) and propidium (18) and with the bifunctional ligands BW284C51 (63) and decamethonium (62) points to only one critical steric clash occurring between the propidium alkyl chain and Lys 57 in Fab410 CDR H2 (data not shown). This observation along with the greater improvement of propidium binding observed for the M70Y mutant of BfAChE compared with its K285D mutant (38) also largely supports our model of the Fab410-EeAChE complex.…”