Protein stability, proteinprotein interactions

1
Protein stability, protein-proteininteractions
11-1
Protein stability - how proteins achieve
stability under extreme conditions (class
presentation) Protein-protein interactions -
recent literature (presentations)
2
Stabilization/destabilization forcesaffecting
proteins
11-2
Any of the forces/structures below could be
stabilizing or destabilizing

• hydrophobic increased strength at higher
  temperatures
• H-bond. mostly stabilizing could
  decrease flexibility
• ionic.. can be attractive or repulsive
• surface residues. major contribution to
  protein stability
• internal residues. major contribution to
  protein stability
• compactness.. can affect stability or
  flexibility
• loops. short loops increases stability
  at higher temperatures
• cavities. presence and size can affect
  stability
• secondary structures. e.g., ß-sheets, a-helices
  more stable than coils
• quaternary structures oligomeric structures can
  be more stable (esp. hetero.)
• ligand binding. e.g., nucleotides,
  cofactors, etc.
• membrane binding major effect(s) on protein
  stability
• protein modifications. modulation of
  conformation, activity, stability, location
• others... temperature, pH, salt, small
  molecules, pressure, etc.

3
Protein stability in different organisms
11-3
4
Surface residues stability vs instability
11-4
thermo-philic
thermo-philic
mesophilic
5
Protein biogenesis/degradationmachineries in
extremophiles
11-5

• Question how do organisms survive at extreme
  temperatures? Do they have more proteins devoted
  to protecting the organism, e.g.,
• molecular chaperones?
• protein folding catalysts?
• proteases?

• Answer the short answer is it doesnt appear to
  be the case
• intrinsic property of proteins

6
protein-protein interactions
11-6