Final answer:
Peptides that bind to a particular MHC isoform have anchor residues which are amino acids that hold the peptide in the peptide-binding groove. The combination of these residues is known as the binding motif.
Step-by-step explanation:
Peptides that bind to a particular MHC isoform usually have either the same or chemically similar amino acids at two to three key positions that hold the peptide tightly in the peptide-binding groove of the MHC molecule. These amino acids are called anchor residues and the combination of these key residues is known as its binding motif.