deGrad(sls-Nano42) is an engineered F-box protein that is designed to target the D. melanogaster sls protein for degradation via the ubiquitin pathway; partial degradation of sls protein has been seen when deGrad(sls-Nano42) was tested in transgenic flies. deGrad(sls-Nano42) contains the N-terminal 198 amino acids of D. melanogaster slmb (this includes the F-box domain), fused to 'Sls-Nano42', a nanobody that binds sls (nanobody raised by immunization using a peptide corresponding to the sls Ig51-Fn2 region) (FBrf0255573).