Abstract
The diverse lipid environment of the biological membrane can modulate the structure and function of membrane proteins. However, little is known about the role that lipids play in modulating protein–protein interactions. Here we employed native mass spectrometry (MS) to determine how individual lipid-binding events to the ammonia channel (AmtB) modulate its interaction with the regulatory protein, GlnK. The thermodynamic signature of AmtB–GlnK in the absence of lipids indicates conformational dynamics. A small number of lipids bound to AmtB is sufficient to modulate the interaction with GlnK, and lipids with different headgroups display a range of allosteric modulation. We also find that lipid chain length and stereochemistry can affect the degree of allosteric modulation, indicating an unforeseen selectivity of membrane proteins toward the chemistry of lipid tails. These results demonstrate that individual lipid-binding events can allosterically modulate the interactions of integral membrane and soluble proteins.
Highlights
The diverse lipid environment of the biological membrane can modulate the structure and function of membrane proteins
As a step toward studying membrane protein and soluble protein interactions, we selected for study the ammonium channel (AmtB) from Escherichia coli (E. coli), an integral membrane protein that is regulated by the soluble trimeric protein GlnK6, 7
We demonstrate for the first time that individual lipidbinding events can allosterically modulate integral membrane and soluble protein interactions
Summary
The diverse lipid environment of the biological membrane can modulate the structure and function of membrane proteins. We employed native mass spectrometry (MS) to determine how individual lipid-binding events to the ammonia channel (AmtB) modulate its interaction with the regulatory protein, GlnK. To determine how individual lipid-binding events modulate the interaction of AmtB with GlnK, we employed native MS, a powerful biophysical technique that has emerged over the past two decades to study proteins and their interactions with ligands[15,16,17,18,19,20]. Thermodynamic parameters for soluble protein–ligand interactions determined using native MS are in agreement with those obtained using other biophysical techniques, such as isothermal titration calorimetry and surface plasmon resonance (SPR)[31, 32] Building upon these recent advances, we use native MS to reveal that individual lipid-binding events allosterically modulate integral membrane protein and soluble protein interactions
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