Studies On Mechanisms Of The Post-Translational Modifications Of Thiopeptides And Their Antibacterial Activities Against Oral Pathogens

OBJECTIVE: Thiopeptides are a class of sulfur-rich peptides with potent antibacterial activity against the Gram-positive bacterium,which have great potential in the treatment of diseases caused by oral pathogens.Nocathiacin I(NOC-I)and nosiheptide(NOS)are two structurally similar thiopeptide members.Comparing with NOS,NOC-I exhibit higher biological activity and additional structural modifications.This study aims to identify the post-translational modifications of NOC-I and evaluate the efficacy of NOS-type analogs against oral pathogens,thus developing improved thiopeptide derivatives for clinical use.CONTENTS AND METHODS: Benefited from the heterologous over expression of the genes noc U and noc V in an engineered Streptomyces actuosus strain SL5001 producing the bicyclic NOS intermediate NOS1260,we subsequently fermented relevant functionalized NOS-type analogs.By characterizing these NOStype analogs’ structure and doing experiments in vitro,we indicated the functions of two cytochrome P450 enzymes Noc U and Noc V.Finally,these NOS derivatives were tested for oral antibacterial activity and structure-activity relationship.RESULTS: We have got three NOS derivatives,and NOS-U shows an extra hydroxyl group at the indole nitrogen;NOS-V1 contains a new hydroxyl group at Cαof the residue Glu6,in contrast with the other product NOS-V2,in which this hydroxyl group is further coupled with the C4 methyl group of the indolic moiety to form an ether linkage.These NOS derivatives exhibit potent antibacterial activities,and NOSV2 shows an improved activity compared with NOS1260.CONCLUSION: These findings provide insights into the catalytic activitiess of the cytochrome P450 enzymes Noc U and Noc V that Noc U is responsible for the Nhydroxylation of the indolic moiety.Noc V appears to act in tandem on two positions in NOS1260 by selectively hydroxylating Glu6 and then oxidatively coupling the indolic moiety,and the ether bond formation has a positive impact on the antibacterial properties of NOS-type thiopeptides.In short,this study is the base of developing novel antibiotics for the prevention and treatment of oral bacterial infection.