Inherently tunable electrostatic assembly of membrane proteins

Area of Science:

• Biophysics
• Structural Biology
• Membrane Protein Science

Background:

• Membrane proteins are crucial for cellular transport.
• Their assembly into ordered structures is vital for function and study.
• Proteorhodopsin (PR) serves as a model system for membrane protein assembly.

Purpose of the Study:

• To investigate the role of electrostatic interactions in the co-assembly of proteorhodopsin (PR) and lipids.
• To demonstrate rational control over PR crystallization using tunable parameters.
• To explore the applicability of these principles to other integral membrane proteins.

Main Methods:

• Tuning recombinant PR variants with modified extramembrane domains and charged amino acid substitutions.
• Varying lipid membrane compositions and lipid-to-PR stoichiometric ratios.
• Analyzing the electrostatic forces governing self-assembly and crystallization.

Main Results:

• Electrostatic interactions were identified as the primary drivers for rapid PR and lipid co-assembly into crystalline arrays.
• Demonstrated rational control over the crystallization process by manipulating protein and lipid properties.
• Showcased the formation of long-range crystalline arrays.

Conclusions:

• Electrostatic forces are key to directed, rapid co-assembly of membrane proteins and lipids.
• The principles elucidated for PR crystallization are generalizable to other integral membrane proteins.
• This work provides a framework for controlling membrane protein assembly and crystallization.