Lecture on Protein Folding and Structure

Introduction

• Folding challenges in everyday life and biology.
• Importance of folding for function beyond convenience.
• Proteins play various roles: channels, structure, enzymes, protection.
• Protein synthesis leads to amino acid chains; further modifications are needed for functionality.

Protein Structure

Primary Structure

• Sequence of amino acids in a protein.
• Amino acids are monomers, building blocks, held by peptide bonds.
• Genes determine amino acid order and number.
• Sequence is critical for protein's structure and function; even one change can affect function (example: sickle cell disease).
• Components: carboxyl group, amino group, and R group (side chain).

Secondary Structure

• Initial folding of amino acid sequences.
• Common structures: alpha helix and beta pleated sheet.
• Folding type depends on amino acid arrangements and hydrogen bonds.
• Focus on backbone, not R groups at this stage.

Tertiary Structure

• 3D shape of a functional protein.
• Importance of R groups (side chains) in folding.
• Variability in R groups affects behavior (hydrophilic or hydrophobic).
• Protein interactions: hydrophilic R groups outside, hydrophobic inside.
• Other influencing interactions: ionic bonds, Van der Waals, disulfide bonds, hydrogen bonds.

Quaternary Structure

• Proteins can consist of multiple polypeptide chains (subunits).
• Interactions like hydrogen and disulfide bonds maintain structure.

Protein Folding

• Proteins fold based on amino acid sequence and interactions.
• Complexity includes intermediate steps.
• "Protein-folding problem" is a research area.
• Chaperonins assist in folding; provide ideal environment.

Importance of Correct Folding

• Correct shape is crucial for function.
• Misfolding related to diseases.
• Environmental factors (temperature, pH) affect protein function and can denature proteins.
  • Denaturation disrupts shape and function.
  • Sometimes reversible, often not.

Conclusion

• Environment affects protein function.
• Importance of maintaining curiosity in understanding biology.