Multivalent interactions mediated in vitro LLPS

Multivalent interactions are a major driving force behind protein liquid-liquid phase separation. Proteins capable of undergoing LLPS owe their multivalency to the presence of intrinsically disordered regions (IDRs). In this study, we purified a protein with one IDR deleted and one remaining IDR, codenamed TF6Δ-GFP, as well as observed its interactions using microscopy with another protein that contains 2 IDRs, codenamed TF9, and is capable of undergoing LLPS. Our results show that TF6Δ-GFP is unable to undergo LLPS alone and has the tendency to self-aggregate. With the addition of TF9, however, TF6Δ-GFP is recruited into TF9 droplets to form TF9-TF6Δ-GFP condensates. TF6Δ-GFP in these condensates were shown to have liquid-like property by Fluorescence recovery after photobleaching (FRAP) experiments, whereas TF6Δ-GFP aggregates are immobile and do not have liquid-like property. In conclusion, multivalent interactions between TF9 and TF6Δ-GFP allowed TF6Δ-GFP to undergo LLPS as well in vitro despite its self-aggregating nature, which may provide insight as to how proteins that aggregate quickly can still have relevant biological function.Bachelor of Science in Biological Science