TAP complex binding

Definition

Target type: molecularfunction

Binding to a TAP complex. [PMID:17947644]

The Transporter Associated with Antigen Processing (TAP) complex is a heterodimer composed of two transmembrane proteins, TAP1 and TAP2, located in the endoplasmic reticulum (ER) membrane. It plays a crucial role in the immune system by transporting peptides generated from cytosolic proteins into the lumen of the ER, where they can be loaded onto major histocompatibility complex (MHC) class I molecules. This process is essential for presenting antigens derived from intracellular pathogens to CD8+ T lymphocytes, triggering an immune response.

The molecular function of TAP complex binding involves the following steps:

1. **Peptide Recognition and Binding:** TAP complex recognizes and binds peptides with specific features, such as a length of 8-10 amino acids and hydrophobic residues at the C-terminus. The peptide binding site is located within the transmembrane domains of TAP1 and TAP2, forming a narrow channel that allows only specific peptides to enter.
2. **ATP-Dependent Transport:** The transport of peptides across the ER membrane is an ATP-dependent process, requiring the hydrolysis of ATP by the ATP-binding cassette (ABC) transporter domains present in both TAP1 and TAP2. The energy from ATP hydrolysis is used to drive the movement of peptides against their concentration gradient, moving them from the cytosol into the ER lumen.
3. **Peptide Editing:** The TAP complex also exhibits a certain level of peptide selectivity, acting as a “peptide editor”. It can preferentially transport peptides with specific features, such as those with higher affinity for MHC class I molecules. This selective transport mechanism ensures that only peptides relevant for antigen presentation are loaded onto MHC class I molecules.
4. **Interaction with Other ER Components:** The TAP complex interacts with other ER proteins, such as tapasin and MHC class I molecules. Tapasin acts as a chaperone protein, facilitating the assembly of MHC class I molecules with peptides transported by TAP. The interaction with MHC class I molecules allows for the efficient loading of peptides onto these molecules, ensuring their proper presentation on the cell surface.

Overall, the molecular function of TAP complex binding involves a sophisticated process of peptide recognition, ATP-dependent transport, peptide editing, and interaction with other ER components. This complex mechanism ensures the efficient and selective presentation of peptides derived from intracellular pathogens to CD8+ T lymphocytes, playing a crucial role in the adaptive immune response.'
"

Proteins (1)

Compounds (8)