proteolipid

Proteolipid is a term used to describe a protein-lipid complex or a protein that has a lipid moiety that anchors or stabilizes it within a membrane. It can refer to proteins that are entirely integrated into lipid bilayers as proteolipid subunits, or to proteins that are covalently modified by lipid attachments. In both cases, the lipid component is essential for the protein’s structure or function and often participates in forming channels, pumps, or enzyme complexes.

Proteolipids are typically small to medium-sized hydrophobic proteins with one or more transmembrane helices, or they may be small proteins that carry a lipid modification such as a myristoyl or palmitoyl group. They frequently assemble with lipids to create specialized membrane environments or to enable efficient energy transduction.

A well-known example is the proteolipid subunits of the F0 sector of ATP synthase. These small hydrophobic polypeptides assemble into a ring that forms part of the proton-conducting pathway and is essential for coupled proton transport and ATP synthesis. Similar proteolipid subunits are found in other energy-transducing complexes across bacteria, archaea, mitochondria, and chloroplasts, reflecting a conserved strategy to combine lipid and protein in membrane function.

Proteolipids are related but distinct from lipoproteins, which are secreted particles carrying lipids in circulation. The study of proteolipids highlights the integral role of lipids not only as membrane material but as functional partners in protein activity.

See also lipoprotein; membrane protein; ATP synthase; proteolipid protein.