A conservative distribution of tridomain NDP-heptose synthetases in actinobacteria

Heptoses are important structural components of Gram-negative bacterium cell wall and participate in bacterial colonization,infection,and immune recognition.Current knowledge of NDP-heptose originating from D-sedoheptulose 7-phosphate in Grampositive bacterium remains limited.Here,in silico analysis suggested that the special tridomain NDP-heptose synthetases with isomerase,kinase,and nucleotidyltransferase activities are conservatively distributed in Actinobacteria class of Gram-positive bacterium.Enzymatical characterization of the tridomain proteins from different strains showed that they are involved in ADPD-glycero-β-D-manno-heptose biosynthesis despite the unexpected discovery of kinase activities deficient in some proteins.The presence of three types of NDP-heptose synthetases in Gram-positive bacterium suggests that it is also a rich source of heptoses and the heptose moieties may play important roles in vivo.Our work updates the understanding of NDP-heptose biosynthesis in Gram-positive bacterium and lays a solid foundation for further physiological function explorations.