Skoltech scientists Maria Tutukina and Mikhail Gelfand have co-authored a recent preprint “Differential Impact of Hexuronate Regulators ExuR and UxuR on the Escherichia coli Proteome”. The work is focused on details of the hexuronic acid metabolism in E. coli. ExuR and UxuR are paralogous proteins belonging to the GntR family of transcriptional regulators. Both are known to control hexuronic acid metabolism in a variety of Gammaproteobacteria. The authors of the work apply 2D difference electrophoresis followed by mass-spectrometry to characterize the changes in the E. coli proteome in response to the uxuR or exuR deletion. Proteomic data clearly show that the effects are different: deletion of uxuR resulted in significantly enhanced expression of D-mannonate dehydratase UxuA and flagellar protein FliC, and inhibition of outer membrane porin OmpF, while the absence of ExuR did not significantly alter the spectrum of detected proteins. This suggests that the roles of proteins predicted as homologs are far from identical. Full text of the preprint is available here.