Paramagnetic proteoliposomes containing a pure, native, and oriented seven-transmembrane segment protein, CCR5.

Area of Science:

• Biochemistry
• Structural Biology
• Virology

Background:

• Seven-transmembrane segment, G protein-coupled receptors are vital in biological processes.
• Characterizing these receptors is challenging due to difficulties in obtaining pure, native protein preparations.
• CCR5 is a key coreceptor for human immunodeficiency virus type 1 (HIV-1) entry.

Purpose of the Study:

• To develop a novel method for characterizing membrane proteins, specifically CCR5.
• To create stable, homogeneous, and oriented preparations of CCR5 for interaction studies.
• To demonstrate the utility of paramagnetic proteoliposomes in studying membrane protein-ligand interactions and antibody selection.

Main Methods:

• Creation of paramagnetic proteoliposomes containing pure and oriented CCR5.
• Utilizing proteoliposomes for binding assays with HIV-1 gp120 envelope glycoprotein and anti-CCR5 antibodies.
• Employing FACS and competition assays with the proteoliposomes.
• Using magnetic properties for rapid buffer exchange and antibody selection from phage display libraries.

Main Results:

• CCR5 proteoliposomes successfully bound HIV-1 gp120 and conformation-dependent antibodies.
• gp120 binding was enhanced by soluble CD4, independent of other cellular proteins.
• Paramagnetic proteoliposomes exhibited uniformity, stability across various conditions, and suitability for FACS and competition assays.
• The method facilitated the selection of CCR5-specific antibodies.

Conclusions:

• Paramagnetic proteoliposomes provide a robust platform for studying membrane protein interactions.
• This technique is valuable for analyzing interactions with both extracellular and intracellular ligands.
• The method is particularly useful for developing screening assays for potential therapeutic inhibitors, such as those targeting HIV-1 entry.