Question

The recognition of tumor antigens by specific cytotoxic T lymphocytes (CTL) is essential for a successful anti-tumor response. These CTL do not react with whole proteins, but recognize peptides generated from intracellular proteins (e.g., proteins overexpressed by tumor cells) that are presented by major histocompatibility complex class I (MHC-1) molecules on the cell surface. In the cytosol, intracellular proteins are degraded to peptide fragments by multicatalytic protease complexes, the proteasomes. For binding and stabilization of MHC-1 molecules these peptides are translocated across the membrane of the endoplasmic reticulum (ER) by the TAP peptide transporter. What is a transmembrane glycoprotein that binds to TAP and to beta-2 microglobulin (after beta-2 has bound the MHC-1 alpha chain) thus acting as a bridge between the MHC-1 molecule and the TAP complex?

Tacrolimus
TLR
TUNEL
Toxoid
Tapasin

Answer 1

The glycoprotein that acts as a bridge between the MHC-1 molecule and the TAP complex is tapasin. It is essential for the antigen processing and presentation pathway which enables CTLs to target and eliminate tumor cells.

Step-by-step explanation:

The transmembrane glycoprotein that binds to the TAP peptide transporter and to beta-2 microglobulin, thereby acting as a bridge between the MHC-1 molecule and the TAP complex, is called tapasin. Tapasin plays a crucial role in the antigen processing and presentation pathway by aiding in the assembly of peptide-MHC class I complexes, which is essential for the recognition of tumor antigens by specific cytotoxic T lymphocytes (CTLs). This process is vital for eliciting an effective anti-tumor immune response as CTLs target and kill cells that present the pathogen-specific antigens on their surfaces.