Sortase-mediatedligation(SML) is a powerfultoolof proteinchemistryallowingthe ligationof peptidescontainingLPxTGsortingmotifs and N-terminalglycinenucleophiles.The installationof a sortingmotif into theproductprohibitsthe assemblyof multiplefragmentsbySML. Here we report multi-fragmentSML based on switch-able sortasesubstrates.Substitutionof the Leu residuebydisulfide-containingCys(StBu)results in active sorting motifs,which are inactivatableby reduction.In combinationwith aphoto-protectedN-Gly nucleophile,multi-fragmentSML isenabledby repetitivecycles of SML and ligationsite switch-ing. The feasibilityof this approachwas demonstratedby aproof-of-conceptfour-fragmentligation,the assemblyofpeptideprobesfor bivalentchromatinbindingproteinsandoligomerizationof peptideantigens.Biochemicaland immu-no-assaysdemonstratedfunctionalityof these probes render-ing them promisingtools for immunologyand chromatinbiochemistry.