Amphipathic polymers: tools to fold integral membrane proteins to their active form

Area of Science:

• Biochemistry
• Structural Biology
• Protein Science

Background:

• Integral membrane proteins (MPs) are crucial for cellular functions but difficult to study due to scarcity and production challenges.
• Overexpressed MPs often form inclusion bodies, hindering the achievement of their native functional 3D structure.
• Detergents and lipids are traditionally used to stabilize MPs, but can interfere with structural and pharmacological studies.

Purpose of the Study:

• To introduce a novel method for folding integral membrane proteins into their native state.
• To demonstrate the utility of amphipol A8-35 as a detergent-free environment for MP structural studies.
• To overcome limitations in studying scarce and difficult-to-produce MPs.

Main Methods:

• Utilized amphipathic polymer, amphipol A8-35, as a novel stabilizing environment for MPs.
• Applied amphipol A8-35 in the absence of detergents or lipids.
• Tested the method on beta-barrel (OmpA, FomA) and alpha-helical (bacteriorhodopsin) membrane proteins.

Main Results:

• Amphipol A8-35 successfully induced both beta-barrel and alpha-helical MPs to fold into their native 3D structures.
• The amphipol facilitated native intramolecular protein-protein interactions over non-native ones.
• Demonstrated feasibility using outer membrane proteins OmpA, FomA, and bacteriorhodopsin.

Conclusions:

• Amphipol A8-35 provides a novel, mild environment for folding integral membrane proteins into their native functional states.
• This approach bypasses the need for detergents or lipids, simplifying MP structural and pharmacological studies.
• The method holds promise for advancing research on diverse integral membrane proteins.