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Ferredoxin-NADP+ Reductase from Pseudomonas putida Functions as a Ferric Reductase
Yeom, Jinki,Jeon, Che Ok,Madsen, Eugene L.,Park, Woojun American Society for Microbiology 2009 Journal of Bacteriology Vol.191 No.5
<B>ABSTRACT</B><P><I>Pseudomonas putida</I> harbors two ferredoxin-NADP<SUP>+</SUP> reductases (Fprs) on its chromosome, and their functions remain largely unknown. Ferric reductase is structurally contained within the Fpr superfamily. Interestingly, ferric reductase is not annotated on the chromosome of <I>P. putida</I>. In an effort to elucidate the function of the Fpr as a ferric reductase, we used a variety of biochemical and physiological methods using the wild-type and mutant strains. In both the ferric reductase and flavin reductase assays, FprA and FprB preferentially used NADPH and NADH as electron donors, respectively. Two Fprs prefer a native ferric chelator to a synthetic ferric chelator and utilize free flavin mononucleotide (FMN) as an electron carrier. FprB has a higher <I>k</I>cat/<I>Km</I> value for reducing the ferric complex with free FMN. The growth rate of the <I>fprB</I> mutant was reduced more profoundly than that of the <I>fprA</I> mutant, the growth rate of which is also lower than the wild type in ferric iron-containing minimal media. Flavin reductase activity was diminished completely when the cell extracts of the <I>fprB</I> mutant plus NADH were utilized, but not the <I>fprA</I> mutant with NADPH. This indicates that other NADPH-dependent flavin reductases may exist. Interestingly, the structure of the NAD(P) region of FprB, but not of FprA, resembled the ferric reductase (Fre) of <I>Escherichia coli</I> in the homology modeling. This study demonstrates, for the first time, the functions of Fprs in <I>P. putida</I> as flavin and ferric reductases. Furthermore, our results indicated that FprB may perform a crucial role as a NADH-dependent ferric/flavin reductase under iron stress conditions.</P>
Sujin Yeom,Jinki Yeom,박우준 한국미생물학회 2010 The journal of microbiology Vol.48 No.2
The zwf, which encodes glucose-6-phosphate dehydrogenase, is repressed by NtrC under nitrogen-limited condition. Previously, we demonstrated that induction of zwf-1 is required for protecting Pseudomonas putida cells under oxidative stress, which could be possible probably because of derepression of HexR on the zwf-1gene under oxidative stress. These findings led us investigate that NtrC still represses the zwf-1 under nitrogen-limited oxidative stress condition, which makes cells more sensitive under such condition. Interestingly, deletion of the ntrC gene significantly reduces growth rate, but renders cells more resistant to oxidative stress, under nitrogen limited condition in P. putida. More vitality of the ntrC mutant under oxidative stress condition was also confirmed by the fluorogenic redox dye using flow cytometry. The results of transcriptome analysis demonstrated that the derepression of several oxidative stress genes along with the zwf-1 gene might confer high resistance to oxidative stress in the ntrC mutant. Here, we presented the data for the first time, showing that different sets of genes are involved in nitrogen-rich and nitrogen-limited oxidative stress conditions and NtrC-sensed nitrogen availability is one of the most important prerequisite for full cellular defense against oxidative stress in P. putida.
Kim, Juhyun,Yeom, Jinki,Jeon, Che Ok,Park, Woojun Microbiology Society 2009 Microbiology Vol.155 No.7
<P>The growth pattern of Pseudomonas putida KT2440 in the presence of glucose and phenylacetic acid (PAA), where the sugar is used in preference to the aromatic compound, suggests that there is carbon catabolite repression (CCR) of PAA metabolism by glucose or gluconate. Furthermore, CCR is regulated at the transcriptional level. However, this CCR phenomenon does not occur in PAA-amended minimal medium containing fructose, pyruvate or succinate. We previously identified 2-keto-3-deoxy-6-phosphogluconate (KDPG) as an inducer of glucose metabolism, and this has led to this investigation into the role of KDPG as a signal compound for CCR. Two mutant strains, the edd mutant (non-KDPG producer) and the eda mutant (KDPG overproducer), grew in the presence of PAA but not in the presence of glucose. The edd mutant utilized PAA even in the presence of glucose, indicating that CCR had been abolished. This observation has additional support from the finding that there is high phenylacetyl-CoA ligase activity in the edd mutant, even in the presence of glucose+PAA, but not in wild-type cells under the same conditions. Unlike the edd mutant, the eda mutant did not grow in the presence of glucose+PAA. Interestingly, there was no uptake and/or metabolism of PAA in the eda mutant cells under the same conditions. Targeted disruption of PaaX, a repressor of the PAA operon, had no effect on CCR of PAA metabolism in the presence of glucose, suggesting that there is another transcriptional repression system associated with the KDPG signal. This is the first study to demonstrate that KDPG is the true CCR signal of PAA metabolism in P. putida KT2440.</P>
Membrane Proteins as a Regulator for Antibiotic Persistence in Gram-Negative Bacteria
Yee Jia Xin,Kim Juhyun,Yeom Jinki 한국미생물학회 2023 The journal of microbiology Vol.61 No.3
Antibiotic treatment failure threatens our ability to control bacterial infections that can cause chronic diseases. Persister bacteria are a subpopulation of physiological variants that becomes highly tolerant to antibiotics. Membrane proteins play crucial roles in all living organisms to regulate cellular physiology. Although a diverse membrane component involved in persistence can result in antibiotic treatment failure, the regulations of antibiotic persistence by membrane proteins has not been fully understood. In this review, we summarize the recent advances in our understanding with regards to membrane proteins in Gram-negative bacteria as a regulator for antibiotic persistence, highlighting various physiological mechanisms in bacteria.
Kim, Young Hoon,Lee, Yunho,Kim, Saehun,Yeom, Jinki,Yeom, Sujin,Seok Kim, Beom,Oh, Sangnam,Park, Sungsu,Jeon, Che Ok,Park, Woojun WILEY-VCH Verlag 2006 Proteomics Vol.6 No.23
<P>This study examined the role of the periplasmic oxidative defense proteins, copper, zinc superoxide dismutase (SodC), and thiol peroxidase (Tpx), from the Shiga toxin-producing Escherichia coli O157:H7 (STEC) in the formation of biofilms. Proteomic analyses have shown significantly higher expression levels of both periplasmic antioxidant systems (SodC and Tpx) in STEC cells grown under biofilm conditions than under planktonic conditions. An analysis of their growth phase-dependent gene expression indicated that a high level of the sodC expression occurred during the stationary phase and that the expression of the tpx gene was strongly induced only during the exponential growth phase. Exogenous hydrogen peroxide reduced the aerobic growth of the STEC sodC and tpx mutants by more than that of their parental strain. The two mutants also displayed significant reductions in their attachment to both biotic (HT-29 epithelial cell) and abiotic surfaces (polystyrene and polyvinyl chloride microplates) during static aerobic growth. However, the growth rates of both wild-type and mutants were similar under aerobic growth conditions. The formation of an STEC biofilm was only observed with the wild-type STEC cells in glass capillary tubes under continuous flow-culture conditions compared with the STEC sodC and tpx mutants. To the best of our knowledge, this is the first mutational study to show the contribution of sodC and tpx gene products to the formation of an E. coli O157:H7 biofilm. These results also suggest that these biofilms are physiologically heterogeneous and that oxidative stress defenses in both the exponential and stationary growth stages play important roles in the formation of STEC biofilms.</P>