Crystal structure of the PHF8 Jumonji domain, an Nepsilon-methyl lysine demethylase.

Crystallographic analysis of the catalytic domain of PHD finger protein 8 (PHF8), an N(epsilon)-methyl lysine histone demethylase associated with mental retardation and cleft lip/palate, reveals a double-stranded beta-helix fold with conserved Fe(II) and cosubstrate binding sites typical of the 2-oxoglutarate dependent oxygenases. The PHF8 active site is highly conserved with those of the FBXL10/11demethylases, which are also selective for the di-/mono-methylated lysine states, but differs from that of the JMJD2 demethylases which are selective for tri-/di-methylated states. The results rationalize the lack of activity for the clinically observed F279S PHF8 variant and they will help to identify inhibitors selective for specific N(epsilon)-methyl lysine demethylase subfamilies.

Ligand supplementation as a method to increase soluble heterologous protein production.

Ligand interactions are central to enzyme or receptor function, constituting a cornerstone in biochemistry and pharmacology. Here we discuss a ligand application that can be exploited to significantly increase the proportion of recombinant protein expressed in soluble form, by including ligands during the culture. Provided that a sufficiently soluble, cell-permeable and avid ligand is available, one can use it to stabilize nascently synthesized proteins, and in this manner promote solubility and prevent aggregation.