The β-barrel structure of GFP contains 11 β-strands. The split-GFP approach uses GFP_1–10, which contains the first 10 β-strands and is expressed in the host cell (and possibly localized to a subcellular compartment). The eleventh strand is attached to the effector molecule of interest, in this case AvrB (AvrB-GFP₁₁). In the cell, the two proteins can reconstitute a fluorescent protein. (Reprinted from Henry et al. [2017], Figure 2A.)