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Effects of 2-monoacylglycerol on in meso crystallization and the crystal structures of integral membrane proteins

DOI: 10.1021/acs.cgd.0c00660 DOI Help

Authors: Luke Smithers (Trinity College Dublin) , Leendert Van Dalsen (Trinity College Dublin) , Coilin Boland (Trinity College, Dublin) , Gerard Reid (Trinity College Dublin) , Dietmar Weichert (Trinity College Dublin) , Martin Caffrey (Trinity College Dublin)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Crystal Growth & Design

State: Published (Approved)
Published: July 2020
Diamond Proposal Number(s): 17810

Abstract: Monoacylglycerols (MAGs) are the lipids most commonly used for crystallizing membrane proteins by the in meso method. The acyl chain and glycerol components of MAGs are ester-linked at the sn-1 hydroxyl of glycerol in 1-MAGs. 1-MAGs succumb to spontaneous transacylation where the chain migrates between the sn-1 and sn-2 hydroxyls. In the mesophase formed by 1-monoolein, the most commonly used MAG, equilibrium is reached in two weeks at 6 mol% 2-monoolein. Variability in 2-MAG content appears in synthetic MAGs produced for the purpose of host lipid screening. In the interests of reproducibility, extensive purification has been implemented to minimize the 2-MAG content of newly synthesized lipid. Here we show, with two membrane proteins, that such efforts are not needed. Specifically, the initial 2-MAG content can vary over wide limits without impacting negatively on the crystallization process or on the structures obtained with those crystals. Dispensing with rounds of purification means that MAGs can be produced using protocols that are simpler, faster, less expensive and more environmentally friendly. An added feature of having 2-monoolein in the crystallization mix is that it stabilizes mesophases with bigger aqueous channels, well suited to structure determination of proteins and complexes with large extramembrane domains.

Journal Keywords: Crystallography; In meso method; Lipid cubic phase; Membrane protein; Monoolein; Synthetic organic chemistry; X-ray crystal structure

Subject Areas: Chemistry, Biology and Bio-materials

Instruments: I24-Microfocus Macromolecular Crystallography

Other Facilities: Swiss Light Source