Study On The Effect Of PAS-LuxR Family Regulators On The Biosynthesis Of Tetramycin And Nystatin In Streptomyces Ahygroscopicus

The secondary metabolism of Streptomycetes ahygroscopicus S91 produces a variety of antibiotics,including the tetraene macrolide antibiotics tetramycin and nystatin.The PAS-LuxR family of regulatory proteins（Ttm RIV and Nys RIV）are present in both tetramycin biosynthesis gene clusters and nystatin biosynthesis,The PAS-LuxR family of regulatory proteins was previously reported to be functionally conserved and complementary,whereas in Streptomycetes ahygroscopicus S91,Nys RIV did not replace the function of Ttm RIV,suggesting that the two proteins are independently regulated in this Streptomyces.The aim of this paper is to investigate the independent regulatory mechanisms of the nys RIV genes by genetic engineering methods such as blocking,back-complementing and overexpressing natural and synthetic genes.Bioinformatics analysis revealed that both Ttm RIV and Nys RIV have a PAS domain at the amino terminus and an HTH motif at the carboxy terminus.t _PASn _HTH and n _PASt _HTH were obtained by cross-fusing the structural domains of these two regulatory proteins.nys RIV,ttm RIV,t _PASn _HTH and n _PASt _HTH all restored tetramycin production inΔnys RIV,while overexpression of nys RIV,ttm RIV,t_PASn _HTH and n _PASt _HTH in Streptomyces containing a single copy amount of the nys RIV gene resulted in a reduction in nystatin production to 60%-90%of that of the starting strain.Overexpression of the nys RIV gene in S91 resulted in the disappearance of nystatin,reduced tetramycin B production to 63%of the starting strain and reduced tetramycin A production to 53%of the starting strain;overexpression of ttm RIV,t _PASn _HTH and n _PASt _HTH resulted in increased tetramycin production.This indicates that Nys RIV is an important regulator of nystatin biosynthesis,and high concentrations of Nys RIV inhibit nystatin biosynthesis,and both the PAS and HTH domains of ttm RIV can improve tetramycin production,and the PAS domain plays a greater role.In this paper,we illustrate the mechanism of PAS-LuxR-regulated protein synthesis by the nys RIV gene on the biosynthesis of nystatin and tetramycin.