Hydrophobic Shielding Preserves Transmembrane Secondary Structure in the Gas Phase.

Area of Science:

• Biochemistry
• Structural Biology
• Computational Biology

Background:

• Electrospray ionization mass spectrometry (ESI-MS) enables gas-phase analysis of intact membrane protein complexes.
• The stability of membrane protein secondary structure after desolvation in ESI-MS is not fully understood.

Purpose of the Study:

• To investigate the stability of membrane protein secondary structure in the gas phase using molecular dynamics (MD) simulations.
• To identify residue-level determinants of transmembrane (TM) domain stability under ESI-MS conditions.

Main Methods:

• Long-time-scale (submillisecond) molecular dynamics (MD) simulations.
• Studied four representative membrane proteins: β-barrel, helix bundle, GPCR, and mechanosensitive channel.
• Analyzed gas-phase stability and residue-level contributions to TM domain integrity.

Main Results:

• Transmembrane (TM) domains of membrane proteins remain stable in the gas phase.
• Local unfolding occurs in extramembrane regions, but TM secondary structure is preserved.
• Hydrophobic interactions and the apolar gas phase environment stabilize TM architecture.

Conclusions:

• The preorganized hydrophobic environment of the membrane and the vacuum stabilize TM secondary structure.
• Surface-exposed hydrophobic residues and oligomeric interfaces are key protectants of TM secondary structure.
• A mechanistic framework is established for membrane protein stability in ESI-MS without lipids.