The purple protein is the extracellular part of the MHC I complex. The yellow peptide is from SARS-CoV-2 and represents the peptide sequence: Arginine-Leucine-Glutamine-Serine-Leucine-Glutamine-Threonine-Tyrosine-Valine (RLQSLQTYV). The blue protein is the extracellular part of the T cell receptor. The complex shows how a specific T cell receptor recognizes the SARS-CoV-2 Spike protein sequence when it is displayed in the MHC I complex. The structure is based on PDB: 7N1E. Read more about this structure: Wu D, Kolesnikov A, Yin R, Guest JD, Gowthaman R, Shmelev A, Serdyuk Y, Dianov DV, Efimov GA, Pierce BG, Mariuzza RA. Structural assessment of HLA-A2-restricted SARS-CoV-2 spike epitopes recognized by public and private T-cell receptors. Nat Commun. 13:19 (2022). DOI: 10.1038/s41467-021-27669-8.
Find out more about how T cells recognize viruses: N. R. Gough, Two pathways to viral recognition. BioSerendipity (1 December 2022) https://www.bioserendipity.com/two-pathways-to-viral-recognition/