Corynebacterium glutamicum is widely used in the production of amino acids.C.glutamicum possesses seven sigma factors,among which SigD is responsible for the transcription of genes involved in the synthesis of mycolic...Corynebacterium glutamicum is widely used in the production of amino acids.C.glutamicum possesses seven sigma factors,among which SigD is responsible for the transcription of genes involved in the synthesis of mycolic acid(MA)and its derivatives,the unique cell envelope of C.glutamicum.To understand the influence of MA synthesis on amino acid production and membrane phenotype of C.glutamicum,the expression of sigD gene and some mycolyltransferase genes,i.e.,cmt1,cop1 and cmt2,were regulated by several growth-regulated promoters in this study.Except for 2 mutant strains of P_(cg3096)-sigD and P_(cg1633)-cop1,the growth and 4-hydroxyisoleucine(4-HIL)titer of most modified strains did not change significantly.But the 4-HIL titer of P_(odhI)-sigD strain increased by 20.73%(142.45±3.69 mM)compared to that of control strain(117.99±0.34 mM).After it was cultivated in bioreactor,4-HIL titer reached 372.56 mM.This may be caused by the increase of MA content,and 17%decrease of cell hydrophobicity and 12%increase of membrane permeability were observed at the exponential phase.In conclusion,we proved that rearrangements in regulation of sigD expression contributed to the improved fermentation performance of C.glutamicum and promoted 4-HIL production.展开更多
Dehydration is one of the key steps in the biosynthesis of mycolic acids and is vital to the growth of Mycobac- terium tuberculosis （Mtb）. Consequently, stalling dehy-dration cures tuberculosis （TB）. Clinically us...Dehydration is one of the key steps in the biosynthesis of mycolic acids and is vital to the growth of Mycobac- terium tuberculosis （Mtb）. Consequently, stalling dehy-dration cures tuberculosis （TB）. Clinically used anti-TB drugs like thiacetazone （TAC） and isoxyl （ISO） as well as flavonoids inhibit the enzyme activity of the β-hydroxy- acyI-ACP dehydratase HadAB complex. How this inhi- bition is exerted, has remained an enigma for years. Here, we describe the first crystal structures of the MtbHadAB complex bound with flavonoid inhibitor butein, 2＇,4,4＇-trihydroxychalcone or fisetin. Despite sharing no sequence identity from Blast, HadA and HadB adopt a very similar hotdog fold. HadA forms a tight dimer with HadB in which the proteins are sitting side-by-side, but are oriented anti-parallel. While HadB contributes the catalytically critical His-Asp dyad, HadA binds the fatty acid substrate in a long channel. The atypical double hotdog fold with a single active site formed by MtbHadAB gives rise to a long, narrow cavity that vertically traverses the fatty acid binding channel. At the base of this cavity lies Cys61, which upon muta- tion to Ser confers drug-resistance in TB patients. We show that inhibitors bind in this cavity and protrude into the substrate binding channel. Thus, inhibitors of MtbHadAB exert their effect by occluding substrate from the active site, The unveiling of this mechanism of inhibition paves the way for accelerating development of next generation of anti-TB drugs,展开更多
According to the previous reports, chromium (Ⅲ) was regarded as the essential component of glucose tolerance factor (GTF) and saccharomyces cerevisiae was one of the richest sources of GTF. It was discovered by Mertz...According to the previous reports, chromium (Ⅲ) was regarded as the essential component of glucose tolerance factor (GTF) and saccharomyces cerevisiae was one of the richest sources of GTF. It was discovered by Mertz (Phys. Rev., 49(1967)) and confirmed by Miesky (Inorg. Biochem., 13(1980)) and Haylock (Exp. Mycol.,展开更多
基金supported by the program of State Key Laboratory of Food Science and Technology(SKLF-ZZA-201904).
文摘Corynebacterium glutamicum is widely used in the production of amino acids.C.glutamicum possesses seven sigma factors,among which SigD is responsible for the transcription of genes involved in the synthesis of mycolic acid(MA)and its derivatives,the unique cell envelope of C.glutamicum.To understand the influence of MA synthesis on amino acid production and membrane phenotype of C.glutamicum,the expression of sigD gene and some mycolyltransferase genes,i.e.,cmt1,cop1 and cmt2,were regulated by several growth-regulated promoters in this study.Except for 2 mutant strains of P_(cg3096)-sigD and P_(cg1633)-cop1,the growth and 4-hydroxyisoleucine(4-HIL)titer of most modified strains did not change significantly.But the 4-HIL titer of P_(odhI)-sigD strain increased by 20.73%(142.45±3.69 mM)compared to that of control strain(117.99±0.34 mM).After it was cultivated in bioreactor,4-HIL titer reached 372.56 mM.This may be caused by the increase of MA content,and 17%decrease of cell hydrophobicity and 12%increase of membrane permeability were observed at the exponential phase.In conclusion,we proved that rearrangements in regulation of sigD expression contributed to the improved fermentation performance of C.glutamicum and promoted 4-HIL production.
文摘Dehydration is one of the key steps in the biosynthesis of mycolic acids and is vital to the growth of Mycobac- terium tuberculosis （Mtb）. Consequently, stalling dehy-dration cures tuberculosis （TB）. Clinically used anti-TB drugs like thiacetazone （TAC） and isoxyl （ISO） as well as flavonoids inhibit the enzyme activity of the β-hydroxy- acyI-ACP dehydratase HadAB complex. How this inhi- bition is exerted, has remained an enigma for years. Here, we describe the first crystal structures of the MtbHadAB complex bound with flavonoid inhibitor butein, 2＇,4,4＇-trihydroxychalcone or fisetin. Despite sharing no sequence identity from Blast, HadA and HadB adopt a very similar hotdog fold. HadA forms a tight dimer with HadB in which the proteins are sitting side-by-side, but are oriented anti-parallel. While HadB contributes the catalytically critical His-Asp dyad, HadA binds the fatty acid substrate in a long channel. The atypical double hotdog fold with a single active site formed by MtbHadAB gives rise to a long, narrow cavity that vertically traverses the fatty acid binding channel. At the base of this cavity lies Cys61, which upon muta- tion to Ser confers drug-resistance in TB patients. We show that inhibitors bind in this cavity and protrude into the substrate binding channel. Thus, inhibitors of MtbHadAB exert their effect by occluding substrate from the active site, The unveiling of this mechanism of inhibition paves the way for accelerating development of next generation of anti-TB drugs,
文摘According to the previous reports, chromium (Ⅲ) was regarded as the essential component of glucose tolerance factor (GTF) and saccharomyces cerevisiae was one of the richest sources of GTF. It was discovered by Mertz (Phys. Rev., 49(1967)) and confirmed by Miesky (Inorg. Biochem., 13(1980)) and Haylock (Exp. Mycol.,
