Solubilisation & purification of membrane proteins using benzylamine-modified SMA polymers

Area of Science:

• Biochemistry and Molecular Biology
• Polymer Chemistry
• Membrane Protein Research

Background:

• Styrene maleic acid co-polymers (SMA) enable membrane protein extraction in their native lipid environment, forming SMA lipid particles (SMALPs).
• SMA2000, a polydisperse polymer, is effective but lacks precise control over length and sequence homogeneity.
• Controlled polymerization techniques like RAFT polymerization offer improved control over polymer characteristics.

Purpose of the Study:

• To develop novel SMA-based polymers with controlled length and homogeneous distribution of hydrophobic moieties for membrane protein solubilization.
• To synthesize and characterize SMA-benzylamine (SMA-BA) polymers using RAFT polymerization and subsequent modification.
• To evaluate the efficiency and stability of different SMA-BA polymer lengths in solubilizing membranes and purifying proteins.

Main Methods:

• RAFT polymerization was used to synthesize a 1:1 styrene:maleic anhydride polymer.
• The polymer was modified with benzylamine to create SMA-benzylamine (SMA-BA) with a 2:1 hydrophobic:hydrophilic ratio.
• SMA-BA polymers of 2, 4, and 7 kDa were synthesized and tested for lipid and membrane solubilization, protein extraction, and stability.

Main Results:

• All tested SMA-BA polymers (2, 4, and 7 kDa) effectively solubilized lipids, cellular membranes, and proteins.
• The 7 kDa polymer showed slower and less efficient membrane solubilization, impacting protein purification yield.
• The 2 kDa polymer offered rapid solubilization but reduced protein stability, while the 4 kDa polymer demonstrated comparable performance to SMA2000, with higher purity.

Conclusions:

• SMA-BA polymers provide a tunable platform for membrane protein extraction, offering better control over polymer length and composition than SMA2000.
• The 4 kDa SMA-BA polymer represents a promising alternative to SMA2000, delivering efficient protein solubilization and enhanced purity.
• SMA-BA polymers exhibit increased sensitivity to Mg2+ ions compared to SMA2000, a factor to consider during application.