The structure of monoacylglycerol lipase from Bacillus sp. H257 reveals unexpected conservation of the cap architecture between bacterial and human enzymes

Abstract

Monoacylglycerol lipases (MGLs) catalyse the hydrolysis of monoacylglycerol into free fatty acid and glycerol. MGLs have been identified throughout all genera of life and have adopted different substrate specificities depending on their physiological role. In humans, MGL plays an integral part in lipid metabolism affecting energy homeostasis, signalling processes and cancer cell progression. In bacteria, MGLs degrade short-chain monoacylglycerols which are otherwise toxic to the organism. We report the crystal structures of MGL from the bacterium Bacillus sp. H257 (bMGL) in its free form at 1.2 Å and in complex with phenylmethylsulfonyl fluoride at 1.8 Å resolution. In both structures, bMGL adopts an α/β hydrolase fold with a cap in an open conformation. Access to the active site residues, which were unambiguously identified from the protein structure, is facilitated by two different channels. The larger channel constitutes the highly hydrophobic substrate binding pocket with enough room to accommodate monoacylglycerol. The other channel is rather small and resembles the proposed glycerol exit hole in human MGL. Molecular dynamics simulation of bMGL yielded open and closed states of the entrance channel and the glycerol exit hole. Despite differences in the number of residues, secondary structure elements, and low sequence identity in the cap region, this first structure of a bacterial MGL reveals striking structural conservation of the overall cap architecture in comparison with human MGL. Thus it provides insight into the structural conservation of the cap amongst MGLs throughout evolution and provides a framework for rationalising substrate specificities in each organism.

Conformational Transition Pathway in the Inhibitor Binding Process of Human Monoacylglycerol Lipase

“…The solution of both open and closed forms of MGL supports the interfacial activation of MGL that allows the enzyme to exist in two main conformational states, an open and a closed forms [15]. Using large-scale MD simulations, Rengachari et al [33] also observed the existence of the stable open and closed conformations of MGL in solution. Furthermore, detailed comparison between the apo and bound forms reveals that the lid-domain undergoes a substantial rearrgemnet upon ligand binding with other regions showing only very small differences [14].…”

“…H257 in the apo form (PDB ID: 3RM3) and in complex with phenylmethylsulfonyl fluoride (PDB ID: 3RLI). Remarkably, the [33].…”

“…Previously, Rengachari et al [33] solved the crystal structures of MGL from the bacterium Basillus sp. H257 in the apo form (PDB ID: 3RM3) and in complex with phenylmethylsulfonyl fluoride (PDB ID: 3RLI).…”

Purification, crystallization and preliminary X-ray diffraction analysis of a soluble variant of the monoglyceride lipase Yju3p from the yeastSaccharomyces cerevisiae

“…H257 have been determined to date (Bertrand et al, 2010;Labar et al, 2010;Schalk-Hihi et al, 2011;Rengachari et al, 2012Rengachari et al, , 2013. The structures revealed an / hydrolase fold with a dynamic yet topologically conserved cap region.…”

Development of novel dyes and fluorescence-imaging based approaches for cellular localization and dynamics of lipid droplets

“…These structures mostly occur as spheroidal macromolecular assemblies having a neutral lipid ester or lipid based polymer core bound by a phospholipid monolayer membrane (Ding et al, 2012;. This is despite the finding of Jacquier et al, (2011) LDs are structurally similar between different groups of organisms, and the enzymes that are responsible for lipid synthesis and degradation are predominantly conserved; for example, monoacylglycerol lipase appears to be conserved between bacteria and humans (Rengachari et al, 2012). LD regulatory proteins are not as widely conserved: for example, the perilipin family, proteins with major roles in LD regulation in animals, are absent from many fungi (Bickel et al, 2009).…”