Protein Folding Protein Folding Proteins have unique 3-dimensional - PowerPoint PPT Presentation

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 nonpolar side 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