Soluble expression and characterization of a mouse epididymis-specific protein lipocalin6

Mouse lipocalin6 (mLcn6) was recently identified to be specifically expressed in the epididymis and speculated to may play a role in sperm maturation. However, further studies were hindered due to the bottleneck to obtain enough recombinant mLcn6 proteins. In this article, GB1 tag was successfully applied to improve the soluble expression of mLcn6. Thermal unfolding experiments demonstrate that GB1 can enhance the structural stability of mLcn6. Fluorescence spectroscopy experiments show that mLcn6 prepared according to our procedure has high affinities to both retinoic acid (K(d)=810nM) and retinol (K(d)=210nM). In conclusion, soluble, stable and active mLcn6 was recombinantly prepared with the help of the GB1 tag, which will facilitate the structural and functional studies of mLcn6.