Improvement o fan E. coli Strain for the heterologous expresión of dTDP-sugar biosynthetic pathways

S. PEIRÚ, E. RODRÍGUEZ Y H. GRAMAJO

Rosario, Argentina

Congreso; XLII Reunión Anual de la Sociedad Argentina de Investigadores en Bioquímica y Biología Molecular (SAIB); 2006

Heterologous expression has become an important tool for polyketide production and combinatorial biosynthesis. Many natural occurring polyketides contain unusual sugars which are essential components of the molecules to be bioactive. Recently we have been able to functionally express in E. coli the biosynthetic pathways of dTDP-mycarose and dTDP-desosamine, using a plasmid-based system, resulting in the production of a fully-glycosylated polyketide antibiotic, Erythromicin C, although in very low levels. These sugars, like many others dTDP-sugars, are synthesized via dTDP-4-keto-6-deoxyglucose (dTKDG) intermediate. In E. coli, the biosynthesis of dTDP-rhamnose, dTDP-VioNAc and dTDP-Fuc4NAc, which are precursors of cell wall components, occurs through the same intermediate dTKDG. Here we have developed an E. coli B host by deleting key genes involved in the biosynthetic pathways of these dTDP-sugars, to improve the expression of new heterologous dTDP-sugar pathways. Deletion of five genes from the biosynthetic pathways of dTDP-rhamnose, dTDP-VioNAc and dTDP-Fuc4NAc resulted in increased intracellular levels of dTKDG. Bioconversion experiments in this new strain expressing the heterologous dTDP-desosamine pathway resulted in highly increased glycosylation levels compared to the parental strain.