PNNL

Biochemists Ernesto Nakayasu and Paul Piehowski, along with EMSL Scientist Jared Shaw, co-authored a recent study in Cell Research that advances what we know about ubiquitin, a regulatory protein found in all eukaryotic organisms, including mammals.

Specifically, the three researchers - in a study led by co-authors at Purdue University - investigated one avenue of a process called ubiquitination. That's when ubiquitin is added to substrate proteins.

Ubiquitination can signal a protein to alter its location, to not interact with other proteins, and even to be recycled, making the ubiquitin network among the most important signaling mechanisms in life.

Ubiquitination is a common target for infectious agents because it helps regulate immunity. The team had shown in a previous paper that the pathogen bacterium Legionella pneumonophila, which causes Legionnaire's disease, produces an enzyme (SdeA) that makes a unique type of ubiquitination in host proteins via a phosphoribose link.

 In this paper they discovered that another protein from Legionella, SidJ, acts as a deubiquitinase. That's an enzyme that plays a role in the infection by "deconjugating" - disrupting - the biological activity of ubiquitin. SidJ is the first deubiquitinase ever described that can deconjugate phosphoribose-linked ubiquitination.

The enzyme may be important in future studies of signaling cascades that have a role in both disease and cellular processes in eukaryotic cells.