Identification and Structure of an MHC Class I-Encoded Protein with the Potential to PresentN-Myristoylated 4-mer Peptides to T Cells.Yamamoto, Y., Morita, D., Shima, Y., Midorikawa, A., Mizutani, T., Suzuki, J., Mori, N., Shiina, T., Inoko, H., Tanaka, Y., Mikami, B., Sugita, M.
(2019) J Immunol 202: 3349-3358
- PubMed: 31043477
- DOI: 10.4049/jimmunol.1900087
- Primary Citation of Related Structures:
- PubMed Abstract:
Similar to host proteins, N -myristoylation occurs for viral proteins to dictate their pathological function. However, this lipid-modifying reaction creates a novel class of "lipopeptide" Ags targeted by host CTLs. The primate MHC class I-enc ...
Similar to host proteins, N -myristoylation occurs for viral proteins to dictate their pathological function. However, this lipid-modifying reaction creates a novel class of "lipopeptide" Ags targeted by host CTLs. The primate MHC class I-encoded protein, Mamu-B*098, was previously shown to bind N -myristoylated 5-mer peptides. Nevertheless, T cells exist that recognize even shorter lipopeptides, and much remains to be elucidated concerning the molecular mechanisms of lipopeptide presentation. We, in this study, demonstrate that the MHC class I allele, Mamu-B*05104, binds the N -myristoylated 4-mer peptide (C14-Gly-Gly-Ala-Ile) derived from the viral Nef protein for its presentation to CTLs. A phylogenetic tree analysis indicates that these classical MHC class I alleles are not closely associated; however, the high-resolution x-ray crystallographic analyses indicate that both molecules share lipid-binding structures defined by the exceptionally large, hydrophobic B pocket to accommodate the acylated glycine (G1) as an anchor. The C-terminal isoleucine (I4) of C14-Gly-Gly-Ala-Ile anchors at the F pocket, which is distinct from that of Mamu-B*098 and is virtually identical to that of the peptide-presenting MHC class I molecule, HLA-B51. The two central amino acid residues (G2 and A3) are only exposed externally for recognition by T cells, and the methyl side chain on A3 constitutes a major T cell epitope, underscoring that the epitopic diversity is highly limited for lipopeptides as compared with that for MHC class I-presented long peptides. These structural features suggest that lipopeptide-presenting MHC class I alleles comprise a distinct MHC class I subset that mediates an alternative pathway for CTL activation.
Laboratory of Cell Regulation and Molecular Network, Graduate School of Biostudies, Kyoto University, Yoshida-Konoe-cho, Sakyo-ku, Kyoto 606-8501, Japan.