Hydrodynamic Analysis of Groucho Q-Domain

The Groucho (Gro)/Transducin-like-enhancer of split (TLE) family of corepressors plays a significant role in the regulation of many cellular processes. Having no intrinsic DNA-binding activity, Gro/TLE interacts with various DNA-bound repressor proteins to repress transcription. Gro/TLE possesses a conserved region known as the Q-domain, and this region has been shown to direct the oligomerization of Gro/TLE, which is required for repression. Although the Q-domain is required for oligomerization, its structural properties have never been fully characterized. Here, the Q-domain was tagged with a small ubiquitin-related modifier protein (SUMO) to alleviate aggregation observed with the untagged Q-domain. Size exclusion chromatography (Gel Filtration) and analytical ultracentrifugations were performed. Results show that SUMO-Q oligomerizes predominantly as a tetramer. However, significant heterogeneity is observed at high salt concentrations. Analysis of the hydrodynamic data suggest a markedly non-spherical structure.