Role of Recurrent Hydrophobic Residues in Catalyzing Helix Formtion by T Cell-presented Pep Tides a Thesis Presented

The overall objective of this study was to understand the mechanisms that control antigen processing and binding of peptides to major histocompatibility complex (MHC) molecules. Towards this goal I investigated (a) the structural features of T cell-presented peptides with a focus on the role recurrent hydrophobic residues catalysis helix formation by these peptides and (b) the biochemical events that determine the fates of the invariant chain molecule (Ii) in its various post-translational processing pathways. In the structural studies, I tested the hypothesis that the recurrence of hydrophobic amino acids in polypeptide positions falling in an axial, hydrophobic strip if the sequence were coiled an a-helix can lead to helical nucleation on hydrophobic surface. For a series of HPLCpurified peptides, including some T cell-presented peptides varying considerably in primary sequence, percentage helicity in the presenc, of lipid vesicles correlated with strip-of-