SpyTagged branched and unbranched K48- and K63-linked Tetra-Ubiquitin chains were immobilized on SpyCatcher agarose (48Ub4; 63Ub4; [Ub]2-48,63Ub-48Ub; [Ub]2-48,63Ub-63Ub). Pulldown were performed from protease-inhibitor treated U2OS cell lines to identify specific binders of K48-K63-branched Ub4.