Membraneeiwitten

Membraneeiwitten are proteins that interact with biological membranes, either embedded in the lipid bilayer or attached to its surface. They are broadly categorized as integral (transmembrane) proteins that span the membrane, peripheral proteins that associate with the membrane via interactions with lipids or other proteins, and lipid-anchored proteins that are covalently attached to a lipid anchor embedded in the bilayer.

Integral membrane proteins may form channels or transporters that move ions and molecules across the membrane, or receptors and enzymes that participate in signaling and metabolism. They often contain hydrophobic transmembrane segments organized as alpha helices or, in some cases, beta-barrels, particularly in the outer membranes of bacteria and in mitochondria.

Functions include selective transport (channels and carriers), signal transduction (receptors such as GPCRs and receptor tyrosine kinases), enzymatic activity on the membrane surface or within the bilayer, cell adhesion, and energy transduction in processes such as photosynthesis and respiration.

Membraneeiwitten are essential for cellular homeostasis and communication. They are major drug targets; many medicinal drugs act by modulating membrane proteins, especially receptors and transporters. Mutations or malfunctions can lead to a wide range of diseases through disrupted signaling, transport, or adhesion.

Structural biology and biophysical approaches such as X-ray crystallography, cryo-electron microscopy, and NMR have elucidated many membraneeiwit structures, though their hydrophobic nature makes study challenging. Detergents, nanodiscs, and lipid environments are used to stabilize them for analysis.