Protein Self Assembly

Protein Shape and Function

• Proteins must be in the correct shape to function properly.
  • Enzymes like maltase require a precise active site for substrate binding.
  • Changing the protein's shape affects the active site, preventing substrate binding.

Denaturation

• Denaturation refers to a protein losing its correct shape.

Causes of Denaturation:

• Heat:
  • High temperatures can denature proteins.
  • The danger of high fever or heat stroke is protein denaturation, which impairs their function.
  • Different proteins denature at different temperatures.
• pH Changes:
  • Ketoacidosis: A condition where excessive ketone production leads to acidic blood.
    • Often seen in poorly controlled diabetics.
    • Can cause behaviors resembling drunkenness due to pH-induced protein dysfunction.
• Chemicals:
  • Certain chemicals can also lead to protein denaturation.

Prions

• Prions are a family of diseases affecting the nervous system.
  • A prion is a denatured protein that gains a new, harmful function.
    • Unlike typical denatured proteins that simply lose function, prions gain a detrimental function.
• Examples:
  • Mad cow disease.
  • Human variant of mad cow disease.
  • Chronic wasting disease in deer.

Anfinsen's Experiment

• Demonstrated that some proteins can spontaneously refold into their correct shape after denaturation.
• Experiment: Heated ribonuclease in a beaker, causing denaturation, then allowed it to cool slowly.
  • The protein refolded into its correct shape without assistance.
• Conclusion: The information for correct folding is inherent in the protein sequence itself.
• Limitation: Not all proteins can self-assemble; some require assistance.