Protein Folding

Protein Background Amino acids are monomers that bond together through peptide bonds to form polypeptides used to build proteins The order of amino acids depends on the sequence of bases in the organism’s DNA Genes code for specific proteins to be built Proteins perform work for the cell

Protein Background cont. Some of the things proteins do: Enzymes that speed up reactions Pigments Building blocks of hair, nails, horns, muscle tissue Immune defense in the form of antibodies

Amino Acid Structure When amino acids bond together the resulting polypeptide chain has an N Terminus and C terminus at either end The R side chains have different chemical structures depending on the amino acid The structure of the R side chain determines how the amino acid will interact with other amino acids and the environment

Amino Acid Properties Hydrophobic = Avoids water, will be tucked into the 3D protein structure Hydrophilic = wants to be near water, will be on the outside of the 3D protein structure Basic = neutralizes acidic amino acids by bonding with them Acidic = neutralizes basic amino acids by bonding with them Other Isoleucine, Leucine, Alanine, Valine, Glycine, Proline, Tryptophan, Phenylalanine Glutamine, Serine, Methionine, Asparagine, Threonine, Tyrosine Histidine, Arginine, Lysine Aspartic Acid (Aspartate), Glutamic Acid (Glutamate) Cysteine = contains sulfur in its side chain causing it to form stabilizing disulfide bridges with other cysteine molecules

1° , 2° , 3° , 4° Structures Primary Structure = the order of amino acids in the polypeptide Secondary Structure = the amino acid chain will interacts with itself to form alpha helix or beta pleated sheet Tertiary Structure = the amino acid chain further interacts with itself to form a 3 dimensional globular shape Quaternary Structure = the polypeptide globs bond together to form an even larger 3D shape

Form = Function The shape of the protein will determine its function

Form = Function cont. If you alter the shape of the protein (due to a mutation in the DNA sequence coding for that protein’s formation) you potentially affect it’s ability to function

Types of Mutations DELETION (a base is lost/deleted) INSERTION (an extra base is added/inserted) Deletion & insertion may cause what’s called a FRAMESHIFT mutation, meaning the reading “frame" changes, thus changing the amino acid sequence from this point forward POINT MUTATION/SUBSTITUTION (one base is substituted for another) If a substitution changes the amino acid, it’s called a MISSENSE mutation If a substitution does not change the amino acid, it’s called a SILENT mutation If a substitution changes the amino acid to a “stop” codon it’s called a NONSENSE mutation