Quantitative in vivo solubility and reconstitution of truncated circular permutants of green fluorescent protein

Several versions of split green fluorescent protein (GFP) fold and reconstitute fluorescence, as do many circular permutants, but little is known about the dependence of reconstitution on circular permutation. Explored here is the capacity of GFP to fold and reconstitute fluorescence from various truncated circular permutants, herein called "leave-one-outs" using a quantitative in vivo solubility assay and in vivo reconstitution of fluorescence. Twelve leave-one-out permutants are discussed, one for each of the 12 secondary structure elements. The results expand the outlook for the use of permuted split GFPs as specific and self-reporting gene encoded affinity reagents.