Styrene–maleic acid (SMA) copolymers comprise styrene and maleic acid in a certain ratio and self-assemble with lipids into nanoparticles called SMA lipid particles (SMALPs). In recent years, SMA copolymers have been used to extract a wide range of membrane proteins from membranes in the form of polymer-bounded nanodiscs. These nanodiscs provide a native environment for membrane proteins, preserving protein function, proper fold and stability. SMALPs are rather compact having the size of 10-30 nm and comprise an effective system for structural and functional characterization of the inserted protein.<br/>Here we report the first solubilization and purification of the full-length nitrate/nitrite sensor histidine kinase NarQ in SMALPs. Histidine kinases constitute one of the most abundant classes of membrane receptors present in all domains of life. Many of these systems are essential for cell growth, survival, or pathogenicity. However, the mechanisms of transmembrane signaling by such sensors are poorly understood due to the lack of structural information of full-length organization of transmembrane sensors.<br/>The results demonstrated that SMA can be used to extract histidine kinases from the membrane with efficiency comparable to, and exceeding that of the commonly used detergent dodecyl maltoside (DDM). SMALP approach offered an increased purity and preservation of the isolated membrane protein in comparison with DDM-based solubilization.

Detergent-free purification of a full-length histidine kinase using styrene-maleic acid copolymers

ACS Spring Meeting 2021

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