Protein Folding

Protein Folding

• Proteins have unique 3-dimensional shapes created by the twisting or folding of one or more polypeptide chains

• The structure of a protein enables it to recognize and bind to other molecules

Protein Folding

Shape Determines Function

Shape Determines Function

Shape Determines Function

Protein Structure

• Primary Structure

• Secondary Structure

• Tertiary Structure

• Quaternary Structure

Primary Structure

• Determined by the sequence of a chain of amino acids held together by peptide bonds

Secondary Structure• Involves regions of coiling (α-helices) or

folding (β-pleated sheets) of the polypeptide

• Stabilized by hydrogen bonds between the carboxyl and amino groups of amino acids

Tertiary Structure

• Results from interactions between the various side chains (R groups)

• Ionic bonds between positive (+) and negative (-) side chains

• Hydrophobic interactions between nonpolarside chains (repelled by water), clump together

• Hydrogen bonds between polar side chains

• Disulfide bridges between the sulfhydryl groups of cysteine amino acids

Tertiary Structure

Quaternary Structure

• Occurs in proteins that are composed of more than one polypeptide

• Results from the combination of hydrogen bonding, ionic bonding, and hydrophobic interactions between polypeptide chains

Protein Folding Control

• Chaperones and proteasomes are molecules that act jointly to regulate protein folding and control the selective removal of misfolded proteins from the cell

• Chaperones control the conformational folding and unfolding of proteins released from ribosomes

• Proteasomes degrade unneeded or damaged proteins

Diseases Caused by Misfolded Proteins

• Alzheimer’s Disease

• Parkinson’s

• Amyotrophic lateral sclerosis (ALS)

• Huntington’s Disease

Sickle-Cell Anemia Mutation

• Causes hemoglobin molecules to crystallize when oxygen levels are low

Insulin Receptor – Type 2 Diabetes