This project comprises the investigation of reversible protein ADP-ribosylation and its impact on bacterial metabolism, using the genetic model of Streptomyces coelicolor A3(2), an industrially important bacterium from the genus Streptomyces, which produces over two-thirds of all clinically useful antibiotics of natural origin. Bacteria, and Streptomyces in particular are known to utilize protein ADP-ribosylation to control a variety of important pathways (such as morphological differentiation and antibiotic production), but the proteins involved in this regulation are mostly unknown (transferases and hydrolases). The goal of this project is the identification and characterization of the enzymes controlling reversible protein ADP-ribosylation, as well as the pathways and protein targets for their regulation in Streptomyces. In addition, we will further analyse the physiological consequences of the inactivation of the corresponding genes. Our studies are expected to provide an important understanding on how Streptomyces and potentially other bacteria control their metabolism and antibiotic production. Based on genomic data and our preliminary biochemical experiments, we uncovered the SCO6450 protein in Streptomyces as a potential protein responsible for reversing the protein mono-ADP-ribosylation. The conservation of this protein from bacteria to human (SCO6450 orthologue in human is called MacroD1) should allow the extension of our conclusions and analyses to the human model. We will employ a combination of biochemistry and cell biology to understand the function of MacroD1 in human cells.