Samino, YolandaLopez, DanielGuil, SaraSaveanu, Loredanavan Endert, Peter MVal, Margarita del2020-04-232020-04-232006-03-10J Biol Chem. 2006 Mar 10;281(10):6358-65. Epub 2006 Jan 6.0021-9258http://hdl.handle.net/20.500.12105/9697Viral antigens complexed with major histocompatibility complex (MHC) class I molecules are recognized by cytotoxic T lymphocytes on infected cells. Assays with synthetic peptides identify optimal MHC class I ligands often used for vaccines. However, when natural peptides are analyzed, more complex mixtures including long peptides bulging in the middle of the binding site or with carboxyl extensions are found, reflecting lack of exposure to carboxypeptidases in the antigen processing pathway. In contrast, precursor peptides are exposed to extensive cytosolic aminopeptidase activity, and fewer than 1% survive, only to be further trimmed in the endoplasmic reticulum. We show here a striking example of a nested set of at least three highly antigenic and similarly abundant natural MHC class I ligands, 15, 10, and 9 amino acids in length, derived from a single human immunodeficiency virus gp160 epitope. Antigen processing, thus, gives rise to a rich pool of possible ligands from which MHC class I molecules can choose. The natural peptide set includes a 15-residue-long peptide with unprecedented 6 N-terminal residues that most likely extend out of the MHC class I binding groove. This 15-mer is the longest natural peptide known recognized by cytotoxic T lymphocytes and is surprisingly protected from aminopeptidase trimming in living cells.engVoRhttp://creativecommons.org/licenses/by-nc-sa/4.0/Amino Acid SequenceAnimalsCarrier ProteinsCell Line, TumorEndoplasmic ReticulumEpitopes, T-LymphocyteHIV Envelope Protein gp160Histocompatibility Antigens Class IApolipoproteinsMiceMice, Inbred BALB CMolecular Sequence DataMutationPeptide FragmentsProtein TransportT-Lymphocytes, CytotoxicTrans-ActivatorsAtribución-NoComercial-CompartirIgual 4.0 Internacional16407287281106358-6510.1074/jbc.M512263200The Journal of biological chemistryopen access