Tertiary structure

Definition

Tertiary structure refers to the overall three-dimensional shape of a protein, formed by the folding and interactions of its polypeptide chain. This structure is critical because it determines the protein's functionality, including how it interacts with other molecules and performs its biological role. Tertiary structure is stabilized by various interactions, such as hydrogen bonds, ionic bonds, hydrophobic interactions, and disulfide bridges, which are essential for proper protein function.

5 Must Know Facts For Your Next Test

1. Tertiary structure is essential for the specific function of proteins, as even slight changes in this structure can result in loss of activity or malfunction.
2. The formation of tertiary structure is driven by the hydrophobic effect, where nonpolar side chains of amino acids cluster away from water, while polar side chains interact with the aqueous environment.
3. Chaperone proteins often assist in the correct folding of proteins into their tertiary structures, preventing aggregation and misfolding.
4. X-ray crystallography and nuclear magnetic resonance (NMR) spectroscopy are common techniques used to determine the tertiary structure of proteins.
5. Diseases like Alzheimer's and cystic fibrosis can be linked to misfolding of proteins, highlighting the importance of correct tertiary structure for health.

Review Questions

• How do various types of interactions contribute to the stability of tertiary structure in proteins?
  • Tertiary structure stability arises from several types of interactions between amino acid side chains. Hydrogen bonds form between polar side chains, while ionic bonds occur between charged groups. Hydrophobic interactions drive nonpolar side chains to cluster together away from water, and disulfide bridges provide covalent links between cysteine residues. These combined interactions create a stable 3D shape essential for the protein's function.
• Discuss the role of chaperone proteins in relation to tertiary structure and protein folding.
  • Chaperone proteins play a crucial role in assisting the proper folding of nascent polypeptide chains into their correct tertiary structures. They help prevent misfolding and aggregation by providing an environment conducive to correct folding. Additionally, chaperones can refold denatured proteins or direct misfolded proteins toward degradation pathways. This ensures that only correctly folded proteins are functional within the cell.
• Evaluate the impact of tertiary structure misfolding on cellular function and disease development.
  • Misfolding of tertiary structures can severely impact cellular functions, leading to loss of protein activity and potentially causing diseases. For example, in Alzheimer's disease, amyloid-beta peptides misfold and aggregate, forming plaques that disrupt neuronal function. Similarly, cystic fibrosis results from a misfolded CFTR protein that cannot reach the cell surface to perform its chloride channel function. These examples illustrate how critical proper tertiary structure is for maintaining cellular health and functionality.

Related terms

primary structure:

The linear sequence of amino acids in a protein, determined by the genetic code.

quaternary structure: The arrangement and interaction of multiple polypeptide chains in a protein complex, which may work together to perform a specific function.

protein folding:

The process through which a polypeptide chain folds into its functional three-dimensional shape, crucial for its activity.