α-helical membrane proteins

Definition

α-helical membrane proteins are integral membrane proteins characterized by their structure, which contains one or more α-helices that span the lipid bilayer of cell membranes. These proteins play crucial roles in various cellular functions, including transport, signaling, and providing structural integrity to membranes, and their helical nature allows them to interact favorably with the hydrophobic environment of the lipid bilayer.

5 Must Know Facts For Your Next Test

1. α-helical membrane proteins often contain hydrophobic amino acids that align with the lipid bilayer, facilitating their insertion and stability within the membrane.
2. These proteins can function as channels or transporters, allowing specific molecules to pass through the membrane based on size and charge.
3. The α-helix structure is stabilized by hydrogen bonds between the backbone atoms, which helps maintain the protein's conformation in a hydrophobic environment.
4. Many G-protein coupled receptors (GPCRs), essential for signal transduction in cells, contain multiple α-helical regions that contribute to their function.
5. Mutations or misfolding in α-helical membrane proteins can lead to various diseases, including cancer and neurological disorders, highlighting their importance in maintaining cellular homeostasis.

Review Questions

• How do α-helical membrane proteins contribute to cellular functions such as transport and signaling?
  • α-helical membrane proteins facilitate transport by forming channels or transporters that allow specific molecules to move across the cell membrane. In signaling, these proteins act as receptors that detect extracellular signals and initiate intracellular responses. Their ability to traverse the lipid bilayer with their helical structure enables them to engage with both the hydrophobic core of the membrane and hydrophilic signaling molecules.
• Discuss the structural features of α-helical membrane proteins and how these features relate to their function within the lipid bilayer.
  • The key structural feature of α-helical membrane proteins is their arrangement of one or more α-helices that span the lipid bilayer. These helices are primarily composed of hydrophobic amino acids, which align well with the hydrophobic environment of the lipid bilayer. This structural adaptation allows them to maintain stability within the membrane while enabling interactions with both extracellular and intracellular environments. The unique orientation and conformation facilitate essential functions like molecule transport and signal transduction.
• Evaluate the impact of mutations in α-helical membrane proteins on human health and disease.
  • Mutations in α-helical membrane proteins can severely disrupt their normal function, leading to a variety of health issues. For instance, alterations in GPCRs can result in improper signaling pathways, contributing to conditions such as cancer or metabolic disorders. Similarly, misfolded transport proteins can cause diseases like cystic fibrosis by impeding ion transport across membranes. Understanding these mutations is critical for developing targeted therapies aimed at correcting or compensating for these dysfunctional proteins.

Related terms

Integral membrane proteins: Proteins that are permanently attached to the membrane and can span across the lipid bilayer, often functioning as receptors or channels.

Lipid bilayer: A double layer of phospholipids that forms the basic structure of cell membranes, creating a hydrophobic environment that separates the internal cellular environment from the external surroundings.

Transmembrane domain: The region of a membrane protein that spans across the lipid bilayer, often composed of one or more α-helices.