CHARACTERISTICS OF ENDOGENOUS PEPTIDES ELUTED FROM THE CLASS-I MHC MOLECULE HLA-B7 DETERMINED BY MASS-SPECTROMETRY AND COMPUTER MODELING

Microcapillary HPLC electrospray ionization tandem mass spectrometry w as used to sequence 15 peptides eluted from HLA-B7. Sequence alignment implicated four peptide positions in specific interactions with the c lass I molecule, and their importance was confirmed using synthetic pe ptides. Because no crystal structure for HLA-B7 was available, compute r-assisted modeling was used to understand novel aspects of peptide bi nding specificity and to accurately predict the effect of defined chan ges in peptide structure. The results demonstrate that mass-spectromet ric sequencing coupled with computer-assisted modeling can be used in the absence of a crystal structure to make accurate predictions concer ning requirements for peptide binding to class I molecules. These tech niques may be valuable to predict or engineer T cell epitopes.