Alpha helices

Definition

Alpha helices are a common structural motif in proteins, characterized by a right-handed coiled or spiral shape formed by hydrogen bonds between the backbone amide and carbonyl groups. This structure is crucial for the stability and functionality of many proteins, allowing them to adopt specific three-dimensional shapes necessary for their biological roles.

5 Must Know Facts For Your Next Test

1. Alpha helices are stabilized by hydrogen bonds between the carbonyl oxygen of one amino acid and the amide hydrogen of another amino acid four residues earlier in the sequence.
2. The average length of an alpha helix is about 10 to 15 amino acids, and they typically rise 1.5 Å in height per residue.
3. In proteins, alpha helices can play a role in forming functional domains and are often found in transmembrane proteins, where they contribute to membrane-spanning regions.
4. Alpha helices can be classified as either left-handed or right-handed, with right-handed being more common in naturally occurring proteins.
5. Certain amino acids, like proline and glycine, can disrupt the formation of alpha helices due to their unique structural properties.

Review Questions

• How do hydrogen bonds contribute to the stability of alpha helices in protein structures?
  • Hydrogen bonds are essential for stabilizing alpha helices by linking the carbonyl oxygen of one amino acid to the amide hydrogen of another amino acid that is four residues earlier. This bonding pattern creates a consistent and strong interaction that helps maintain the helical shape. The regularity and strength of these hydrogen bonds are key factors that allow alpha helices to form stable and functional regions within proteins.
• What role do alpha helices play in the overall structure and function of proteins?
  • Alpha helices are crucial components of protein secondary structure that help define the overall conformation and functionality of proteins. They often provide structural support and can facilitate interactions with other molecules, allowing proteins to perform their biological roles effectively. The specific arrangement of alpha helices contributes to the formation of active sites and binding pockets within enzymes and receptors, thereby influencing their activity and specificity.
• Evaluate how disruptions in alpha helix formation might impact protein function and what implications this could have on cellular processes.
  • Disruptions in alpha helix formation can lead to misfolding or instability of proteins, which can severely affect their function. For example, if an essential enzyme loses its helical structure, it may fail to bind substrates properly or catalyze reactions efficiently. This misfolding could lead to cellular dysfunction and contribute to diseases such as Alzheimer's or cystic fibrosis, highlighting the importance of proper protein folding and structure for maintaining cellular health.

Related terms

Protein folding: The process by which a protein assumes its functional three-dimensional shape from a linear chain of amino acids.

Secondary structure: The local folded structures that form within a protein due to hydrogen bonding, including alpha helices and beta sheets.

Hydrogen bonding: A type of weak chemical bond that is important for the stabilization of the alpha helix structure in proteins.