Lecture 3-2: Membrane Proteins

Membrane Proteins

Proteins that perform multiple functions including transporters, anchors, receptors, and enzymes associated with cell membranes.

Transmembrane Proteins

Proteins that span the entire lipid bilayer and have faces on either side of the membrane.

Hydrophobic Residues

Amino acid side chains that do not interact favorably with water; key for membrane protein insertion.

Aqueous Pore Proteins

Proteins that create hydrophilic spans across membranes allowing the passage of hydrophilic molecules.

Amphipathic Detergents

Detergents like SDS and Triton X-100 that can release membrane proteins by covering hydrophobic regions.

X-ray Crystallography

Classic method for determining protein structure requiring ordered crystal formation for X-ray scattering.

Cryo-Electron Microscopy

Modern proteomics method revealing the structure of membrane proteins, allowing visualization without the need for crystallization.

Cell Cortex

A network of proteins that supports cell shape by interacting with the cytoskeleton and membrane proteins.

Glycosylation

The process where sugars are attached to proteins and lipids on the plasma membrane.

Lectins

Proteins that bind specific sugar patterns, playing a role in cell recognition and immune response.

Fluorescence Recovery After Photobleaching (FRAP)

Method to measure protein diffusion by observing the recovery of fluorescence in bleached membrane areas.

Epithelial Cells

Cells that form sheets attached to a basal lamina and exhibit polarity with restricted protein regions.

Diffusion Barriers

Structural features that restrict protein movement in the plasma membrane, forming specialized functional domains.

Glycocalyx

A sugar coating on cells that provides protection and mediates cell recognition.

Bacteriorhodopsin

A light-driven proton transporter found in Halobacterium halobium, important for understanding membrane protein function.

Integral Membrane Proteins

Proteins that are directly associated with the membrane, either spanning it completely or partially.

Peripheral Membrane Proteins

Proteins that are indirectly associated with the membrane, often through interactions with integral proteins.