Tris(hydroxymethyl)aminomethane Linker-Bearing Triazine-Based Triglucosides for Solubilization and Stabilization of Membrane Proteins

Abstract

High-resolution membrane protein structures are essential for a fundamental understanding of the molecular basis of diverse cellular processes and for drug discovery. Detergents are widely used to extract membrane-spanning proteins from membranes and maintain them in a functional state for downstream characterization. Due to limited long-term stability of membrane proteins encapsulated in conventional detergents, development of novel agents is required to facilitate membrane protein structural study. In the current study, we designed and synthesized tris(hydroxymethyl)aminomethane linker-bearing triazine-based triglucosides (TTGs) for solubilization and stabilization of membrane proteins. When these glucoside detergents were evaluated for four membrane proteins including two G protein-coupled receptors, a few TTGs including TTG-C10 and TTG-C11 displayed markedly enhanced behaviors toward membrane protein stability relative to two maltoside detergents [DDM (n-dodecyl-β-d-maltoside) and LMNG (lauryl maltose neopentyl glycol)]. This is a notable feature of the TTGs as glucoside detergents tend to be inferior to maltoside detergents at stabilizing membrane proteins. The favorable behavior of the TTGs for membrane protein stability is likely due to the high hydrophobicity of the lipophilic groups, an optimal range of hydrophilic–lipophilic balance, and the absence of cis–trans isomerism.

Melamine-cored glucosides for membrane protein solubilization and stabilization: importance of water-mediated intermolecular hydrogen bonding in detergent performance

“…As for the MGs, the optimal alkyl chain length was observed to be C11, the same alkyl chain length found in other detergent studies. 23,32,59,62,63 MG-C11 was more effective than DDM at stabilizing all tested membrane proteins. Furthermore, this detergent conferred enhanced stability to two GPCRs (b 2 AR and MOR) compared to LMNG and TTG-C11.…”

“…One important factor determining detergent efficacy for protein stabilization is the hydrophobicity of the detergent hydrophobic group. 32 The presence of a small number of polar groups (e.g., amino and hydroxyl groups) in the detergent lipophilic region could be detrimental for membrane protein stability, as these weaken detergent interactions with membrane protein surfaces (i.e., protein-detergent interactions). As a result, detergents including amino functional group(s) in the detergent core or lipophilic region are rarely used for membrane protein study.…”

“…30 These biochemical tools are particularly effective for structural elucidation of biologically and pharmaceutically important bio-macromolecules such as G protein-coupled receptors (GPCRs) and ATP-binding cassette (ABC) transporters, highlighting significant contributions of novel detergents to membrane protein structure determination. Very recently, we reported a couple of classes of 1,3,5-triazine-based detergents including triazine-based di-maltosides (TEMs), 31 tris(hydroxymethyl)methanamine (TRIS)-bearing triazine-based glucosides (TTGs), 32 and triazine-based tetra-maltosides (TZMs) 33 for membrane protein stability. In this study, we report another class of 1,3,5-triazine-based amphiphiles containing a melamine unit (2,4,6-triamino-1,3,5-triazine) in the central region, denoted as melamine-cored glucosides (MGs).…”