deGradFP (degrade Green Fluorescent Protein) is a method for inactivating GFP-tagged proteins. A single-domain antibody fragment against GFP (vhhGFP4) is fused to the F-box domain from the slmb protein N-terminus (Nslmb) and expressed under UAS control. The fusion protein binds GFP and directs it to the proteasome for degradation. If gene function is provided only by a GFP fusion construct, expression of Nslmb-vhhGFP4 protein from P{UAS-Nslmb-vhhGFP4} results in loss-of-function phenotypes in GAL4-expressing cells.

Reference: Caussinus et al. (2011). Fluorescent fusion protein knockout mediated by anti-GFP nanobody. Nat. Struct. Mol. Biol. 19: 117--121.