PROCESSING AND DELIVERY OF PEPTIDES PRESENTED BY MHC CLASS-I MOLECULES

Effective MHC class I peptide loading requires the proteolytic degrada tion of cytosolic proteins and the TAP-mediated translocation of pepti des across the membrane of the endoplasmic reticulum. The proteasome i s emerging as the main cytosolic protease generating class I binding p eptides. The recent elucidation of the proteasome crystal structure, t ogether with the use of functional inhibitors, has enhanced our unders tanding of proteasome function. Genetic analysis of a novel mutant cel l line emphasizes the importance of the TAP-class I interaction in the assembly of mature class I heterotrimers, and suggests that additiona l MHC-encoded components are required.