Minor pocket B influences peptide binding, peptide presentation and alloantigenicity of H-2Kb.
Microsequence analysis of peptides eluted from the murine class I H-2Kb molecule together with the three-dimensional structure of the molecule co-crystallized with a homogeneous population of peptides suggests that pocket B is a minor pocket that does not play a major role in peptide presentation. This is in contrast to most other class I molecules in which pocket B plays a central role in selecting and presenting antigenic peptides. To investigate the role of pocket B in antigen presentation by the Kb molecule, we analyzed site-directed mutants of position 45 in pocket B for their effect on both allo- and peptide-specific recognition. We made an identical set of mutations in Kbm8 at residue 45 in order to evaluate their influence in the context of a more open pocket B which results from the bm8 substitution at amino acid 24 (E-->S). We demonstrated that this minor pocket did play a significant role in the antigenicity of both molecules and that this role was more readily apparent in the context of the more open pocket B of Kbm8. In addition, we found that some substitutions of residue 45 in the Kbm8 molecule restored recognition by some alloreactive and peptide specific anti-Kb T cell clones which are normally restricted to Kb, indicating that multiple configurations of amino acids in a pocket could result in similar binding and presentation capabilities.
Yun
T J
TJ
Department of Immunology, Mayo Foundation, Rochester, MN 59905.
Tallquist
M D
MD
Rohren
E M
EM
Sheil
J M
JM
Pease
L R
LR
D000595:Amino Acid Sequence; D000818:Animals; D017951:Antigen Presentation / Q000276:immunology*; D003602:Cytotoxicity, Immunologic; D006183:H-2 Antigens / Q000235:genetics / Q000276:immunology*; D007519:Isoantigens / Q000276:immunology*; D008285:Major Histocompatibility Complex / Q000235:genetics / Q000276:immunology; D051379:Mice; D008809:Mice, Inbred C3H; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009842:Oligopeptides / Q000235:genetics / Q000276:immunology*; D010047:Ovalbumin / Q000235:genetics / Q000276:immunology; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology; D014721:Vesicular stomatitis Indiana virus / Q000276:immunology; D014764:Viral Proteins / Q000276:immunology*
D006183:H-2 Antigens; C032876:H-2Kb protein, mouse; D007519:Isoantigens; D009842:Oligopeptides; D014764:Viral Proteins; D010047:Ovalbumin