Lecture Notes: Quaternary Structure of Proteins

Introduction

• Presenter: Mr. Lim
• Topic: Quaternary Structure of Proteins
• Focus: Understanding the concept and interactions within quaternary structures

Quaternary Structure Overview

• Definition: Combination of multiple proteins into a larger complex protein
• Components: Held together by various interactions (e.g., hydrogen bonding, ionic interactions, dipole-dipole interactions)

Comparisons to Other Structures

• Tertiary vs Quaternary:
  • Tertiary: Interactions occur between amino acids on the same protein
  • Quaternary: Interactions occur between different proteins
• Types of Interactions in Structures:
  • Secondary Structure: Hydrogen bonds between peptide links
  • Tertiary Structure: Hydrogen bonds between side chains of amino acids on the same protein
  • Quaternary Structure: Hydrogen bonds between side chains of amino acids on different proteins

Diagram Explanation

• Green Protein Example:
  • A protein with multiple hydrogen bonds holding its structure together within the same protein
  • Quaternary structure involves interactions between lengths of different proteins

Complementary Shapes

• Requirement:
  • Proteins must have complementary shapes for interactions to occur
  • Must be close enough to form multiple interactions
  • Interactions are specific at the atomic level
• Examples:
  • If shapes do not match precisely, interactions will not hold, and proteins will fly apart

Formation of Larger Complex Proteins

• Multiple identical proteins can join to form a complex protein
• Example:
  • Protein 1, Protein 2, and Protein 3 with the same shape can fit together due to quaternary interactions

Summary

• Quaternary interactions are similar to tertiary interactions (possibly including disulfide links) but occur between different proteins
• These interactions create larger and more complex protein structures