Membrane Proteins Lecture Notes

Flashcards for reviewing protein and membrane structures.

Amino Acid Structure

An alpha carbon connected to an amino group, a carboxyl group, an H, and an R group.

Zwitterion

A molecule with both positive and negative electrical charges, but the net charge is zero.

Nonpolar Amino Acids

Amino acids with hydrophobic side chains, including Glycine, Alanine, Valine, Leucine, Isoleucine, Methionine, Phenylalanine, Tryptophan, and Proline.

Polar Amino Acids

Amino acids with hydrophilic side chains, including Serine, Threonine, Cysteine, Tyrosine, Asparagine, and Glutamine.

Electrically Charged Amino Acids

Amino acids with charged side chains, including Aspartic acid, Glutamic acid, Lysine, Arginine, and Histidine.

Peptide Bond

A covalent chemical bond linking two consecutive amino acid monomers along a peptide or protein chain.

Levels of Protein Structure

Primary (amino acid sequence), Secondary (α-helices and β-sheets), Tertiary (3D folding), and Quaternary (multiple polypeptide subunits).

Primary Structure

The sequence of amino acids determined directly by inherited genetic information.

Secondary Structure

Results from hydrogen bonds forming α-helices and β-sheets.

Alpha Helix

Intrachain bonding with backbone carbonyl oxygen bonds with an amide hydrogen on the fourth residue further toward the C-terminus. Right handed turns.

Beta Sheet

Interstrand binding where hydrogen bonds are between backbone molecules. Strands can run parallel or antiparallel.

Tertiary Structure

3D folding with hydrogen bonds, hydrophobic interactions, van der Waals interactions, disulfide bridges, and ionic bonds.

Protein Domains

Distinct regions within the tertiary structure, which often have specific functions.

Quaternary Structure

Multiple polypeptide subunits (e.g., Hemoglobin).

Molecular Chaperones

Assist in the proper folding of proteins.

Membrane Protein Types

Integral Proteins, Peripheral Proteins, and GPI-anchored Proteins

Membrane Properties

Fluid, asymmetric, specific to function, self-assembling, mosaic, and semi-permeable.

Integral Membrane Proteins

Proteins embedded within the lipid bilayer.

Peripheral Membrane Proteins

Proteins associated with the membrane surface.

GPI-Anchored Protein

Proteins linked to the membrane via a glycosylphosphatidylinositol (GPI) anchor.

Removing Membrane Proteins

Can be achieved using nonionic detergents to solubilize the proteins.

Detergent-solubilized Protein

A membrane protein that is removed from the membrane using nonionic detergents.

Fusion of Mouse and Human Cells

Illustrates the fluid property of the cell membrane.

FRAP (Fluorescence Recovery After Photobleaching)

A method to measure the fluidity of the cell membrane.