specificity-analysis-protein-lysine-methyltransferases-using-spot

Specificity Analysis of Protein Lysine Methyltransferases Using SPOT Peptide Arrays

Lysine methylation is an emerging post-translation modification and it has been identified on several histone and non-histone proteins, where it plays ...

Stuttgart University

In the yeast Saccharomyces cerevisiae, key regulatory enzymes of gluconeogenesis such as fructose-1,6-bisphosphatase are degraded via the ubiquitin proteasome system when cells are replenished with glucose. Polyubiquitination is carried out by the Gid complex, a multisubunit ubiquitin ligase that consists of seven different Gid (glucose-induced degradation-deficient) proteins. Under gluconeogenic conditions the E3 ligase is composed of six subunits (Gid1/Vid30, Gid2/Rmd5, Gid5/Vid28, Gid7, Gid8, and Gid9/Fyv10). Upon the addition of glucose the regulatory subunit Gid4/Vid24 appears, binds to the Gid complex, and triggers ubiquitination of fructose-1,6-bisphosphatase. All seven proteins are essential for this process; however, nothing is known about the arrangement of the subunits in the complex. Interestingly, each Gid protein possesses several remarkable motifs (e.g. SPRY, LisH, CTLH domains) that may play a role in protein-protein interaction. We, therefore, generated altered versions of individual Gid proteins by deleting or mutating these domains and performed co-immunoprecipitation experiments to analyze the interaction between distinct subunits. Thus, we were able to create an initial model of the topology of this unusual E3 ubiquitin ligase.

Exploring the topology of the Gid complex, the E3 ubiquitin ligase involved in catabolite-induced degradation of gluconeogenic enzymes.

New protein lysine methyltransferase (PKMT) assays are needed to facilitate screening for improved PKMT inhibitors, because PKMTs are mutated or overexpressed in several cancers. In cells, methylated lysine residues are recognized by reading domains such as the chromodomain of HP1β, which bind to target proteins in a lysine-methylation-specific manner. Herein we describe a sensitive, robust, and non-radioactive high-throughput PKMT assay that employs the HP1β chromodomain to detect the methylation of peptide substrates by the human SUV39H1 and SUV39H2 PKMTs. The assay has a very good dynamic range and high signal-to-noise ratio. It can be used to screen for PKMT inhibitors, as illustrated by analyzing the inhibition of SUV39H1 by chaetocin. The IC50 value of this inhibition was found to be 480 nM, which is close to its published value. Our data indicate that natural reading domains can be used as alternates to methyl-specific antibodies in PKMT assays. Reading domains can be produced recombinantly in E. coli at low cost and consistent quality, and they are accessible to protein design.

Article	Year
Exploring the topology of the Gid complex, the E3 ubiquitin ligase involved in catabolite-induced degradation of gluconeogenic enzymes. The Journal of biological chemistry\| PubMed ID: 22645139	2012
Non-radioactive protein lysine methyltransferase microplate assay based on reading domains. ChemMedChem\| PubMed ID: 23671032	2014

Denis Kusevic

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