Orange boxes represents the RLC sequence (UniProtKB, P02612). Blue boxes represent the SpyTag002 sequence (VPTIVMVDAYKRYK, (Keeble et al. 2017)), black line represents GSGESG linker, and the yellow box represents the SpyCatcher002 sequence (Keeble et al. 2017). Lengths of boxes reflect approximate relative sequence lengths. A) QD-RLC (RLC = 20 kDa), QD (blue circle/star) attached to RLC at Cys-108. B) Spy-RLC, SpyTag on N-terminus of RLC. C) RLC-Spy, SpyTag on C-terminus of RLC. D) RLC-SpyC, SpyCatcher (15.5 kDa) fused to the C-terminus of RLC via a 2X length linker (34.6 kDa).