ligand-gated monoatomic ion channel activity

Definition

Target type: molecularfunction

Enables the transmembrane transfer of an ion by a channel that opens when a specific ligand has been bound by the channel complex or one of its constituent parts. [GOC:mtg_transport, ISBN:0815340729]

Ligand-gated monoatomic ion channel activity describes the process by which a specific molecule, known as a ligand, binds to a channel protein, triggering a conformational change that opens the channel and allows the passage of a single type of ion across the cell membrane. These channels are crucial for rapid communication within and between cells, playing roles in diverse biological processes.

Here's a detailed description of the molecular function:

1. **Ligand Binding:** The process initiates with the binding of a specific ligand to a binding site on the channel protein. This binding event is highly selective, ensuring that only the appropriate ligand can activate the channel. The ligand can be a neurotransmitter, a hormone, a drug, or even a change in the membrane potential.

2. **Conformational Change:** Upon ligand binding, the channel protein undergoes a conformational change. This alteration in the protein's three-dimensional structure is essential for opening the channel. The conformational change can be subtle, involving only a small shift in the protein's conformation, or it can be more dramatic, involving a large-scale rearrangement of the protein's structure.

3. **Channel Opening:** The conformational change exposes a pore or channel through the cell membrane, allowing ions to pass through. The pore is typically lined with charged amino acid residues, creating an electrostatic environment that favors the passage of specific ions.

4. **Ion Flow:** The opening of the channel creates a pathway for ions to move across the membrane down their electrochemical gradient. This movement of ions can have a profound impact on the cell's electrical potential, leading to changes in cell excitability, signaling, and other cellular functions.

5. **Desensitization:** After a period of prolonged ligand binding, the channel may become desensitized, reducing its ability to open. This desensitization mechanism helps to prevent overstimulation of the cell and ensures that the channel does not remain permanently open.

6. **Ligand Dissociation:** Eventually, the ligand will dissociate from the binding site, causing the channel to close. The channel returns to its closed conformation, restoring the membrane's ion permeability to its original state.

Examples of Ligand-gated monoatomic ion channels:

- **Nicotinic acetylcholine receptor (nAChR):** Found in neuromuscular junctions and the brain, this channel is activated by the neurotransmitter acetylcholine. It allows the passage of sodium and potassium ions, contributing to muscle contraction and neuronal signaling.

- **GABA receptors:** These channels are activated by the neurotransmitter gamma-aminobutyric acid (GABA). They allow the passage of chloride ions, leading to hyperpolarization of neurons and inhibition of neuronal activity.

- **Glycine receptors:** These channels are activated by the neurotransmitter glycine. They allow the passage of chloride ions, similar to GABA receptors, contributing to inhibition of neuronal activity.

In summary, ligand-gated monoatomic ion channel activity is a highly specific and regulated process that enables rapid and precise communication within and between cells. These channels play crucial roles in numerous biological functions, including neuronal signaling, muscle contraction, and sensory perception. Their dysfunction can lead to various diseases, highlighting their importance for human health.'
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Proteins (10)

Compounds (222)