REGULATED CIRCUITS INVOLVED WITH pH - REGULATED GENE EXPRESSION IN Salmonella typhimurium

Iel Soo Bang,Yong Keun Park,John W . Foster 생화학분자생물학회 1993 생화학분자생물학회 춘계학술발표논문집 Vol.- No.-

Session K : Prokaryotic Gene Structure and Expression : SIGNAL TRANSDUCTION RELATED TO PATHOGENESIS OF SALMONELLA TYPHIMURIUM

Iel Soo Bang,Seong Ho Bang,In Soo Lee,Yong Keun Park,Yung Nok Lee 한국생화학분자생물학회 (구 한국생화학회) 1993 추계학술대회집 Vol.- No.-

Streptococcus mutans Strains Isolated in Korea Can Hardly Metabolize Exogenous Nitric Oxide

Hwa Jeong Lee,Iel Soo Bang 대한구강생물학회 2015 International Journal of Oral Biology Vol.40 No.4

Cariogenic Streptococcus mutans encounters a variety of host defense factors produced in oral cavity. Nitric oxide (NO) and NO-mediated reactive nitrogen species are potential antimicrobials of innate immunity that can threaten the fitness of S. mutans in their ecological niches. Streptococcal strategies to detoxify cytotoxic NO, which allow S. mutans to persist in caries or other environments of the oral cavity, remain unknown. In this study, we directly measured NO consumption rates of S. mutans isolated in Korea. Surprisingly, all S. mutans strains were unable to consume exogenous NO efficiently, while an intracellular parasite Salmonella enterica serovar Typhimurium expressing the NO-metabolizing enzyme flavohemoglobin consumed most of the NO. This result suggested that S. mutans has alternative detoxification systems for tolerating NO-induced nitrosative stresses.

Acid stress activation of the &sgr;^E stress response in <i>Salmonella enterica</i> serovar Typhimurium

Muller, Cé,cile,Bang, Iel-Soo,Velayudhan, Jyoti,Karlinsey, Joyce,Papenfort, Kai,Vogel, Jö,rg,Fang, Ferric C. Blackwell Publishing Ltd 2009 Molecular microbiology Vol.71 No.5

<P>Summary</P><P>The alternative sigma factor &sgr;<SUP>E</SUP> is activated by unfolded outer membrane proteins (OMPs) and plays an essential role in <I>Salmonella</I> pathogenesis. The canonical pathway of &sgr;<SUP>E</SUP> activation in response to envelope stress involves sequential proteolysis of the anti-sigma factor RseA by the PDZ proteases DegS and RseP. Here we show that &sgr;<SUP>E</SUP> in <I>Salmonella enterica</I> sv. Typhimurium can also be activated by acid stress. A &sgr;<SUP>E</SUP>-deficient mutant exhibits increased susceptibility to acid pH and reduced survival in an acidified phagosomal vacuole. Acid activation of &sgr;<SUP>E</SUP>-dependent gene expression is independent of the unfolded OMP signal or the DegS protease but requires processing of RseA by RseP. The RseP PDZ domain is indispensable for acid induction, suggesting that acid stress may disrupt an inhibitory interaction between RseA and the RseP PDZ domain to allow RseA proteolysis in the absence of antecedent action of DegS. These observations demonstrate a novel environmental stimulus and activation pathway for the &sgr;<SUP>E</SUP> regulon that appear to be critically important during <I>Salmonella</I>–host cell interactions.</P>

Molecular Cloning and Genetic Characterization of the nadC Gene , Which Encodes a Quinolinic Acid Phosphoribosyltransferase in Salmonella Typhimurium

Jin Hee Kim,Iel Soo Bang,Sang Kyun Koh,Yong Keun Park,Yung Nok Lee 한국미생물생명공학회 ( 구 한국산업미생물학회 ) 1992 한국미생물생명공학회 학술발표초록집 Vol.1992 No.1

Characterization of an Extracytoplasmic Chaperone Spy in Protecting Salmonella against Reactive Oxygen/Nitrogen Species

Yoon Mee Park,Hwa Jeong Lee,Iel Soo Bang KOREAN ACADAMY OF ORAL BIOLOGY 2014 International Journal of Oral Biology Vol.39 No.4

Antimicrobial actions of reactive oxygen/nitrogen species (ROS/RNS) derived from products of NADPH oxidase and inducible nitric oxide (NO) synthase in host phagocytes inactivate various bacterial macromolecules. To cope with these cytotoxic radicals, pathogenic bacteria have evolved to conserve systems necessary for detoxifying ROS/RNS and repairing damages caused by their actions. In response to these stresses, bacteria also induce expression of molecular chaperones to aid in ameliorating protein misfolding. In this study, we explored the function of a newly identified chaperone Spy, that is localized exclusively in the periplasm when bacteria exposed to conditions causing spheroplast formation, in the resistance of Salmonella Typhimurium to ROS/RNS. A spy deletion mutant was constructed in S. Typhimurium by a PCR-mediated method of one-step gene inactivation with λ Red recombinase, and subjected to ROS/RNS stresses. The spy mutant Salmonella showed a modest decrease in growth rate in NO-producing cultures, and no detectable difference of growth rate in H2O2 containing cultures, compared with that of wild type Salmonella. Quantitative RT-PCR analysis showed that spy mRNA levels were similar regardless of both stresses, but were increased considerably in Salmonella mutants lacking the flavohemoglobin Hmp, which are incapable of NO detoxification, and lacking an alternative sigma factor RpoS, conferring hypersusceptibility to H2O2. Results demonstrate that Spy expression can be induced under extreme conditions of both stresses, and suggest that the protein may have supportive roles in maintaining proteostasis in the periplasm where various chaperones may act in concert with Spy, thereby protecting bacteria against toxicities of ROS/RNS.

Response Regulator RssB의 활성 조절

박희정,방일수,Park, Hee Jeong,Bang, Iel Soo 한국미생물학회 2013 미생물학회지 Vol.49 No.3

많은 세균들은 환경적 스트레스에 대항하기 위해 세균 생존에 유용한 특정 유전자들의 전사를 유도하는 대체시그마 인자 RpoS를 활용한다. 세포 내 RpoS 단백질의 농도는 주로 ClpXP 단백질 분해효소의 조절을 통해 결정된다. RpoS를 ClpXP로 전달하기 위해서는 adaptor 단백질 RssB가 반드시 필요하다. Two-component-type response regulator RssB는 RpoS와 지속적으로 상호작용을 하지만, 다양한 환경변화에 의해 RssB-RpoS 상호작용이 억제되어 세균에서 RpoS 양을 증가시킨다. 본 총설에서는 최근까지 연구 된 RssB-RpoS 상호작용에 관여하는 RssB의 anti-adaptor 단백질 IraD, IraM, IraP 등의 조절인자들과 RssB의 N-terminal 수용체 도메인의 인산화에 대해 설명하고 요약하였다. 이러한 RssB의 정교한 활성을 통한 RpoS 분해조절 과정은 외부환경 스트레스로부터 보다 효율적으로 세균을 보호할 수 있다. Against environmental stresses, many bacteria utilize the alternate sigma factor RpoS that induces transcription of the specific set of genes helpful in promoting bacterial survival. Intracellular levels of RpoS are determined mainly by its turnover through proteolysis of ClpXP protease. Delivery of RpoS to ClpXP strictly requires the adaptor protein RssB. The two-component-type response regulator RssB constantly interacts with RpoS, but diverse environmental changes inhibit this interaction through modification of RssB activity, which increases RpoS levels in bacteria. This review discusses and summarizes recent findings on regulatory factors in RssB-RpoS interactions, including IraD, IraM, IraP anti-adaptor proteins of RssB and phosphorylation of N-terminal receiver domain of RssB. New information shows that the coordinated regulation of RssB activity in controlling RpoS turnover confers efficient bacterial defense against stresses.

외부 무기인 농도 변화에 의해 조절되는 pst pit 돌연변이 살모넬라주의 arg 및 art 유전자 전사

박윤미 ( Yoon Mee Park ),방일수 ( Iel Soo Bang ) 조선대학교 치의학연구원 2013 Oral Biology Research (Oral Biol Res) Vol.37 No.2

Purpose: Salmonella enterica serovar Typhimurium (S. Typhimurium) can cause salmonellosis, including gastroenteritis and systemic infection in animal hosts such as humans by diet contamination. To replicate and survive in an animal host, S. Typhimurium must compete against host cells for nutrients. Inorganic phosphate (Pi) is an essential element for all organisms and is used for cellular signal transduction and synthesis of various biomolecules. Thus, systems for uptake and homeostasis of Pi are required for cell metabolism. Uptake of Pi in S. Typhimurium is mainly regulated by components of the high-affinity adenosine triphosphate-binding cassette-transport system Pst and low-affinity transporter Pit. To identify genetic factors contributing to homeostasis of Pi, this study investigated the transcriptional profiles of Salmonella mutants lacking Pst and Pit transporters experiencing changes in extracellular Pi. Materials and Methods: Transcriptome of pst pit mutant S. Typhimurium in response to low (0.1 mM) and high (10 mM) extracellular Pi were compared by cDNA microarray analysis, respectively. Results: The results show that transcription of argI encoding ornithine carbamoyltransferase and artJ encoding arginine third transport system was significantly induced. Conclusion: Data suggest a relationship between arginine metabolism and Pi homeostasis in S. Typhimurium.

세균의 인산 항상성: 인산 수송 단백질들의 역할

박윤미,방일수,Park, Yoon-Mee,Bang, Iel-Soo 한국미생물학회 2012 미생물학회지 Vol.48 No.2

인은 인지질, 탄수화물 및 핵산 등의 생분자 합성에 필요한 원소이다. 세균은 외부환경으로부터 인산이나 인산을 포함하는 영양소를 흡수하여 인을 얻고, 세포대사에 사용되고 남은 인산은 polyphosphate 형태로 저장한다. 현재까지 알려진 다섯 개의 인산 수송 시스템 중, 인산에 특이적으로 높은 친화력을 갖는 Pst 시스템이 가장 중요한 역할을 하며, 그 발현은 세포외부 인산 농도에 반응하는 PhoB-PhoR two component 신호전달 시스템에 의해 조절된다. 반응 조절 단백질 PhoB는 인산 대사뿐 아니라 이와 관계없는 유전자들의 전사를 조절하는 것으로 알려졌으며, 따라서 PhoB의 활성이 조절되지 않으면 많은 종류의 다른 표현형이 나타난다. 본 총설은 각 인산 수송 시스템의 기능이 결여된 세균의 표현형에 대한 최근 연구 결과를 토대로 다음과 같은 내용을 기술하였다. 첫째, 세포 내부 인산의 적정 농도 유지를 위한 인산 수송 시스템들의 역할, 둘째, 인산뿐 아니라 여타 환경 신호와 관련된 수송 시스템의 다양한 표현형, 그리고 마지막으로, 수송 시스템들 간 혹은 그 조절자들 간의 표현형 중복을 분류하여 제시하였다. 이러한 내용은 결국 세균의 대사, 적응반응 및 병원성 발현에 미치는 인산 항상성의 중요성을 강조한다. Phosphorous is an essential element for the synthesis of various biomolecules including phospholipids, carbohydrates and nucleic acids. Bacterial cells can uptake it as forms of phosphate and phosphate-containing nutrients from extracellular environments, and reserve extra phosphate to polyphosphate inside the cell. Among five phosphate transport systems, Pst plays central roles in phosphate transport, and its expression is coordinated by the regulation of PhoB-PhoR two component signal transduction system in response to extracellular levels of phosphate. Genomic studies on the response regulator PhoB reveal many genes independent of phosphate metabolism. Based on recent findings on phenotypes of bacteria lacking proper function of each phosphate transport system, this review discusses roles of phosphate transporters in maintaining optimum intracellular phosphate levels, and presents diverse phenotypes of phosphate transporters related with other environmental signals as well as phosphate, then finally points out functional redundancy among phosphate transport systems or their regulators, which emphasize importance of phosphate homeostasis in governing metabolism, adaptation, and virulence of bacteria.

The Membrane-Bound Transcriptional Regulator CadC Is Activated by Proteolytic Cleavage in Response to Acid Stress

Lee, Yong Heon,Kim, Ji Hye,Bang, Iel Soo,Park, Yong Keun American Society for Microbiology 2008 Journal of Bacteriology Vol.190 No.14

<B>ABSTRACT</B><P>Proteolytic processes often participate in signal transduction across bacterial membranes. In <I>Salmonella enterica</I> serovar Typhimurium, the transcriptional regulator CadC activates genes of lysine decarboxylase system in response to external acidification and exogenous lysine. However, the signaling mechanism of CadC activation remains unexplored. We report here that CadC is located on the inner membrane under normal growth conditions but rapidly cleaved under acid stress conditions, leading to the induction of target gene transcription. As full-length CadC is degraded, the N-terminal fragment containing the DNA-binding domain accumulates in the inner membrane. Moreover, we show that C-terminal truncations of CadC abolish its degradation, resulting in complete loss of activator function. Together, these observations suggest that site-specific proteolysis at the periplasmic domain of CadC generates a biologically active form of N-terminal DNA-binding domain to promote target gene activation.</P>