<prompt> The peptide binding site on Class I MHC molecules is located in:Proximal domain of a subunitsDistal domain of a subunitProximal domains of a and p subunitDistal domains of a and p subunit  <response>: Major histocompatibility complex MHC molecules are found in one region of chromosome 6. They are divided into class I and class II. Peptide binding site on class I MHC molecules is located in a grove between the distal domains of a subunits between a1 a 2 domains. CD8 Cytotoxic T lymphocytes can recognize peptide antigen only when presented along MHC I molecules. Ref: Interface between Chemistry and Biochemistry By Pierre Jolles, Page 106; Textbook of Microbiology By Ananthanarayan and Panicker, 7th Edition, Page 130. 