MHC class I protein binding

Definition

Target type: molecularfunction

Binding to a major histocompatibility complex class I molecule; a set of molecules displayed on cell surfaces that are responsible for lymphocyte recognition and antigen presentation. [GOC:jl]

MHC class I proteins are cell surface receptors that present peptide antigens to cytotoxic T lymphocytes (CTLs). This process, known as antigen presentation, is crucial for the immune system's ability to recognize and eliminate infected or cancerous cells. The molecular function of MHC class I protein binding involves a complex interplay of interactions between the MHC molecule, the peptide antigen, and the T cell receptor (TCR).

1. **Peptide Binding:** MHC class I molecules have a groove that binds to short peptides (typically 8-10 amino acids long) derived from intracellular proteins. These peptides can be derived from viral, bacterial, or tumor proteins, or from normal cellular proteins that are processed through the proteasome. The binding of peptides to MHC class I molecules is highly specific and depends on the amino acid sequence of the peptide.

2. **Assembly and Trafficking:** MHC class I molecules are assembled in the endoplasmic reticulum (ER) with the help of chaperone proteins. The peptide-binding groove is initially occupied by a chaperone protein called tapasin. When a peptide binds to the MHC I molecule, tapasin dissociates, and the MHC I-peptide complex is transported to the cell surface.

3. **TCR Recognition:** Once at the cell surface, the MHC I-peptide complex can interact with the TCR on CTLs. The TCR is a heterodimer consisting of an alpha and a beta chain that recognizes specific peptide-MHC I complexes. This recognition event triggers a signal transduction cascade within the CTL, leading to the activation of the CTL and the destruction of the target cell.

4. **Immune Response:** The binding of MHC I molecules to TCRs on CTLs initiates an immune response against cells presenting foreign peptides. CTLs release cytotoxic molecules such as perforin and granzyme, which induce apoptosis in the target cell. This process eliminates infected or cancerous cells and prevents the spread of disease.

In summary, the molecular function of MHC class I protein binding involves the presentation of peptide antigens to CTLs, the recognition of these antigens by TCRs, and the subsequent activation of CTLs to eliminate infected or cancerous cells. This process is essential for the adaptive immune system's ability to fight disease.'
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Proteins (3)

Compounds (66)