MCB: Protein Folding and Molecular Chaperones

lack specific tertiary structures
- high polar residues
- low nonpolar

non globular state is preferred

proteins that are unfolded but become ordered when bound to their target protein

- Permanently unfolded proteins
- Transient

polypeptide chain gets correct 3D structure --> biologically active native state

highly cooperative process

so many combinations of residues but not enough time

important intermediate in the folding pathway

- incorrect disulfide bonds
- proline residues
- clustering of intermediates bc of hydrophobic groups

- enzymes that assist formation of proper disulfide bonds during folding
- Incorrect disulfide bonds are on protein surface

- Enzymes that catalyzes trans to cis changes in selected (any amino acid)-Proline peptide
- Cis proline very essential
- PPI speed up slow process of trans --> cis

- proteins that prevent and reverse any inappropriate interactions
- most are ATPases
- known as "heat shock" proteins

HSP 70, Chaperonin, HSP90, Nucleoplasmins

- early life of proteins (ribosomes)

- acts when protein is fully synthesized
- form large barrel shape complex

Protein will be degraded

- Proteasomes
- Lysosomes

highly selective

non selective

Ubiquitin: protein that acts as a tag for targeting other proteins for degradation
Proteasome: large protein complex that degrades proteins

Ubiquitin Activating Enzyme
- Using the energy from ATP to form a thioester bond between its Cys and Cterminal

Ubiquitin Conjugating Enzyme
- Transferring the activated ubiquitin from E1 to its own Cys residue

Ubiquitin Ligase
- Transferring the activated ubiquitin from E2 to a lysine residue in a protein substrate