Final answer:
The peptide binding groove of MHC Class I molecules is formed by the α1 and α2 domains of the α chain, with the β2 microglobulin helping to stabilize the structure. This groove is crucial for presenting antigens to T cells, an important step in the immune response.
Step-by-step explanation:
The peptide binding groove of MHC Class I molecules is composed of the α chain, which contains three domains: α1, α2, and α3. However, the actual peptide binding groove is formed by just two of these domains, α1 and α2. The third domain, α3, along with a smaller protein called β2 microglobulin, stabilizes the structure on the membrane but does not directly participate in peptide binding.
The binding groove of MHC I molecules is essential for the function of major histocompatibility class (MHC) I molecules, which present antigen molecules to T cells. This presentation is critical for the immune system in identifying and destroying infected or abnormal cells. This is in contrast to the cleft of MHC Class II molecules, which involves the α1 and β2 domains and is typically expressed on antigen-presenting cells such as macrophages, dendritic cells, and B cells.