• 한국미생물·생명공학회지
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• 제38권4호
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• pp.349-361
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• 2010

본 총설에서는 아미노산의 공업적 생산균인 Corynebacterium glutamicum의 탄소 대사 및 이와 관련된 총체적 조절 메커니즘에 대한 최근의 연구를 정리하였다. C. glutamicum의 산업적 발효을 위한 기질로서 사용되는 당밀은 주로 sucrose, glucose, fructose로 이루어져 있으며, 이들 당은 phosphotransferase system을 통해서 수송된다. C. glutamicum의 탄소 대사 특징은 glucose가 다른 당이나 유기산 등과 함께 존재할 때, glucose와 이러한 탄소원 들을 동시에 대사한다. 그러나 glucose/glutamate 혹은 glucose/ethanol 등의 혼합물에서 는 탄소원의 순차적 이용으로 인해 나타나는 diauxic growth 현상을 나타내며, 이러한 carbon catabolite repression(CCR) 현상은 E. coli나 B. subtilis 등에서 알려진 것과는 다른 독특한 분자적 메커니즘과 조절 circuits을 가지고 있음이 밝혀지고 있다. C. glutamicum의 CRP homologue인 GlxR은 acetate 대사를 포함하여 glycolysis, gluconeogenesis 및 TCA cycle 등을 포함하는 중심탄소대사 조절 뿐만 아니라, 다양한 세포 기능의 조절에 관여하는 총체적 조절 단백질로서의 역할이 제시되고 있다. C. glutamicum의 adenylate cyclase(AC)는 막과 결합된 class IIIAC 로서, 막 단백질의 특성상 아직 규명되어 있지 않은 세포 외부의 환경 변화에 대응하여 세포 내의 cAMP합성 수준을 조절할 수 있는 sensor로 추정할 수 있다. 특히 C. glutamicum의 경우 배지내 glucose 를 비롯한 탄소원과 cAMP 농도와의 관련성이 E. coli에서 알려진 교과서적 지식과는 상반되게 변화하는 경향을 보이고 있어, cAMP signaling에 의한 세포 내 regulatory network 등은 향후 풀어야 할 의문으로 남아있다. 탄소대사 조절의 최상위에 존재하며 global 조절자인 GlxRcAMP 복합체 이외에도 차상위 전사조절 단백질로서 RamB, RamA, SugR 등이 존재하여 다양한 탄소대사를 조절한다. 최근 들어서는 새로운 탄소원으로서 대두되고 있는 biomass 관련 기질들을 이용할 수 있는 C. glutamucum 균주 구축을 통하여 이용 기질의 범위를 확대시키고자 하는 연구 및 탄소 대사와 관련하여 L-lysine의 발효 수율 혹은 생산성을 향상시키고자 하는 다양한 분자적 균주 육종 연구 등이 수행되고 있다.

• 한국토양비료학회지
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• 제33권4호
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• pp.253-260
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• 2000

Agrobacterium tumefaciens에 존재하는 Ti 플라스미드의 virulence(vir)유전자들은 상처난 식물세포에서 분비되는 페놀화합물에 의해서 발현이 유도된다. 본 연구에서는 3종류의 A. tumefaciens들을 대상으로 8종의 페놀화합물들 중에서 vir유전자의 발현에 영향을 미치는 페놀 화합물들의 종류와 이들 균주에서 발현되는 vir유전자의 활성을 조사하였다. A. tumefaciens MW102에 존재하는 vir유전자는 4-hydroxyacetophenone, phenol, catechol, resorcinol과 vanillin등 5종류의 페놀화합물들에 의해서 높게 발현된 반면, 다른 A. tumefaciens Mw105와 Mw108의 vir유전자들은 이들 페놀화합물들에 의해서 매우 낮게 발현되거나 또는 발현되지 않았다. 또한 A. tumefaciens Mw102는 A. tumefaciens Mw105와 Mw108의 vir유전자를 매우 높게 발현시키는 acetosyringene에 의해서는 매우 낮게 발현되었다. 따라서 vir유전자의 발현을 유도시키는 능력은 Ti 플라스미드들의 종류와 페놀화합물들의 종류에 따라서 서로 다르다는 결과를 얻었다. 결과적으로 vir유전자 유도능력의 차이는 vir A 유전자에서 발현되는 sensor단백질의 차이 때문일 것으로 사료된다.

• 센서학회지
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• 제15권4호
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• pp.237-244
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• 2006

Atomic force microscope (AFM) has become a common tool for the structural and physical studies of biological macromolecules, mainly because it provides the ability to perform experiments with samples in a buffer solution. In this study, structure of proteins and nucleic acids has been studied in their physiological environment that allows native intermolecular complexes to be formed. Cr and Au were deposited on p-Si (100) substrate by thermal evaporation method in sequence with the thickness of $200{\AA}$ and $500{\AA}$, respectively, since Au is adequate for immobilizing biomolecules by forming a self-assembled monolayer (SAM) with semiconductor-based biosensors. The SAM, streptavidin and biotin interacted each other with their specific binding energy and their adsorption was analyzed using the Bio-AFM both in a solution and under air environment. A silicon nitride tip was used as a contact tip of Bio-AFM measurement in a solution and an antimony doped silicon tip as a tapping tip under air environment. Actual morphology could also be obtained by 3-dimensional AFM images. The length and agglomerate size of biomolecules was measured in stages. Furthermore, $R_{a}$ (average of surface roughness) and $R_{ms}$ (mean square of surface roughness) and surface density for the adsorbed surface were also calculated from the AFM image.

• 한국정보전자통신기술학회논문지
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• 제2권2호
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• pp.9-14
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• 2009

본 연구에서는 유헬스용 요분석기를 개발하기 위한 선행 연구로서 요분석 스트립의 색변화를 측정할 수 있는 정색반응 전자회로를 개발하였다. 정색반응 시스템은 컴퓨터, 정색반응 전자회로, 트레이장치, 센서조합체 및 소프트웨어로 구성하였다. 요분석 스트립의 색 변화를 측정하기 위하여 칼라센서가 사용되기 때문에, 표준 색상지를 이용하여 칼라센서의 측정값과 RGB값 사이의 선형방정식을 수립하였다. 빨간색(R)의 회귀방정식은 $Red=0.2414{\times}x$(센서 값) - 3.0042($R^2=0.9801$)로 나타났고, 녹색(G)의 회귀방정식은 $Green=0.2857{\times}x$(센서 값) - 6.4251($R^2=0.9868$)로 나타났고, 파란색(B)의 회귀방정식은 $Blue=0.2114{\times}x$(센서 값) - 6.2743($R^2=0.9837$)으로 나타났으므로 표준색상지와 칼라센서는 높은 상관관계가 있는 것을 알 수가 있었다. 정색반응 시스템을 검증하기 위하여 요 성분 중 적혈구, 빌리루빈, 우로빌리노겐, 케톤, 단백질의 5가지 성분에 대하여 각기 다른 농도로 표준시약을 제조하여 정색반응을 측정하였다. 각 시약의 농도에 따른 칼라센서의 정색반응 결과가 통계적으로 타당한 결과를 보였고 유헬스용 요분석기 개발에 적용할 수 있을 것으로 사료된다.

• Journal of Photoscience
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• 제9권2호
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• pp.281-283
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• 2002

S-modulin in frog or its bovine homologue, recoverin, is a 26 kDa EF-hand $Ca^{2+}$-binding protein found in rod photoreceptors. The $Ca^{2+}$ -bound form of S-modulin binds to rhodopsin kinase (Rk) and inhibits its activity. Through this regulation, S-modulin is believed to modulate the light-sensitivity of a rod. In the present study, we tried to identify the interaction site of the $Ca^{2+}$ -bound form of S-modulin to Rk. First, we mapped roughly the interaction regions by using partial peptides of S-modulin. The result suggested that a specific region near the amino terminus is the interaction site of S- modulin. We then identified the essential amino acid residues in this region by using S-modulin mutant proteins: four amino acid residues were suggested to interact with Rk. These residues are located in a small closed pocket in the $Ca^{2+}$-free, inactive form of S-modulin, but exposed to the surface of the molecules in the $Ca^{2+}$ -bound, active form of S-modulin. Two additional amino acid residues were found to be crucial for the $Ca^{2+}$ -dependent conformational changes of S-modulin. The present study firstly identified the functional site of S-modulin, a member of a neuronal calcium sensor protein family.in family..

• Molecules and Cells
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• 제26권2호
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• pp.193-199
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• 2008

The pro-apoptotic Bcl-2 family member Bim acts as a sensor for apoptotic stimuli and initiates apoptosis through the mitochondrial pathway. To identify novel regulators of Bim, we employed the yeast two-hybrid system and isolated the human gene encoding macrophage migration inhibitory factor (MIF), a ubiquitously expressed proinflammatory mediator that has also been implicated in cell proliferation, the cell cycle and carcinogenesis. The interaction between MIF and Bim was confirmed by both in vitro and in vivo protein interaction assays. Intriguingly, protein complexes between MIF and the three major Bim isoforms (BimEL/BimL/BimS) could be detected in HEK293 and K562 cells, especially in cells undergoing apoptosis. Moreover, exogenous expression of MIF partially inhibited Bim-induced apoptosis in HEK293 cells. SiRNA-mediated knockdown of MIF increased apoptosis in K562 cells exposed to the chemical oxidant diamide. Endogenous MIF may regulate the pro-apoptotic activity of Bim and inhibit the release of cytochrome c from mitochondria.

• Smart Structures and Systems
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• 제8권1호
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• pp.17-37
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• 2011

The microcantilever (MCL) sensor is one of the most promising platforms for next-generation label-free biosensing applications. It outperforms conventional label-free detection methods in terms of portability and parallelization. In this paper, an overview of recent advances in our understanding of the coupling between biomolecular interactions and MCL responses is given. A dual compact optical MCL sensing platform was built to enable biosensing experiments both in gas-phase environments and in solutions. The thermal bimorph effect was found to be an effective nanomanipulator for the MCL platform calibration. The study of the alkanethiol self-assembly monolayer (SAM) chain length effect revealed that 1-octanethiol ($C_8H_{17}SH$) induced a larger deflection than that from 1-dodecanethiol ($C_{12}H_{25}SH$) in solutions. Using the clinically relevant biomarker C-reactive protein (CRP), we revealed that the analytical sensitivity of the MCL reached a diagnostic level of $1{\sim}500{\mu}g/ml$ within a 7% coefficient of variation. Using grazing incident x-ray diffractometer (GIXRD) analysis, we found that the gold surface was dominated by the (111) crystalline plane. Moreover, using X-ray photoelectron spectroscopy (XPS) analysis, we confirmed that the Au-S covalent bonds occurred in SAM adsorption whereas CRP molecular bindings occurred in protein analysis. First principles density functional theory (DFT) simulations were also used to examine biomolecular adsorption mechanisms. Multiscale modeling was then developed to connect the interactions at the molecular level with the MCL mechanical response. The alkanethiol SAM chain length effect in air was successfully predicted using the multiscale scheme.

• 원예과학기술지
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• 제30권3호
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• pp.243-249
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• 2012

Hexokinase is the first enzyme in the hexose assimilation pathway; it acts as a sensor for plant sugar responses, and it is also important in determining the fruit sugar levels. The full-length cDNA of a hexokinase gene was isolated from loquat through reverse transcription polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends, which was designated as EjHXK1. EjHXK1 is 1,839 bp long and contains an entire open reading frame encoding 497 amino acids. The predicted protein of EjHXK1 shares 72%-81% similarity with other plant hexokinases. Phylogeny analysis indicated that EjHXK1 is closely related to maize and rice hexokinases. Transient expression of the 35S: EjHXK1-GFP fusion protein was observed on the cell membrane and cytoplasm. Real-time RT-PCR indicated that EjHXK1 is expressed in loquat leaves, stems, flowers, and fruits. EjHXK1 transcripts were higher during early fruit development, but decreases before maturation, which is consistent with hexokinase enzyme activity during fruit development and conducive for hexose accumulation in mature fruits. These results imply that EjHXK1 may play important roles in the regulation of sugar flux during fruit ripening.

• BMB Reports
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• 제31권6호
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• pp.565-571
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• 1998

The expression of the endogenous human apolipoprotein(apo)E gene was significantly induced when HepG2 cells were treated with exogenous 25-hydroxy-cholesterol. This sterol-mediated apoE gene upregulation appears to require the participation of a positive element for the apoE gene transcription (PET) ( -169/ -140), a core sequence of upstream regulatory element (URE)1 enhancer of the human apoE gene. This PET was renamed as sterol regulatory element (SRE)4 based on its new role as a sensor for the level of intracellular sterol. Furthermore, a gel mobility shift analysis showed that binding activity of the SRE4 binding protein (BP) obtained from HepG2 cells was induced by sterol treatment, while that from either MCF7 or BT20 cells remained unchanged. Binding activity of SRE4BP was also induced in mouse macrophage cells, J774A.1, by sterol treatment, but it was drastically reduced when cells were subjected to treatment of AY-9944, a potent inhibitor for sterol synthesis. However, binding activity of Spl, which is a co-binding protein to the SRE4 region, remained the same in either condition, suggesting that SRE4BP (formally known as PETBP) may be mainly responsible for the sterol-mediated regulation of the apoE gene expression. Deletion analysis of the core binding site of SRE4BP by gel mobility shift assays showed that the minimal sequence of the SRE4BP binding appears to reside between -157 and -140, confirming the identity of SRE4 with the previously determined core sequence of URE1.

• Journal of Microbiology and Biotechnology
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• 제27권11호
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• pp.2037-2043
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• 2017

The surface protein hemagglutinin (HA) mediates the attachment of influenza virus to host cells containing sialic acid and thus facilitates viral infection. Therefore, HA is considered as a good target for the development of diagnostic tools for influenza virus. Previously, we reported the isolation of single-stranded aptamers that can distinguish influenza subtype H1 from H5. In this study, we describe a method for the selective electrical detection of H1 using the isolated aptamer as a molecular probe. After immobilization of the aptamer on Si wafer, enzyme-linked immunosorbent assay (ELISA) and field emission scanning electron microscopy (FE-SEM) showed that the immobilized aptamer bound specifically to the H1 subtype but not to the H5 subtype. Assessment by cyclic voltammetry (CV) also demonstrated that the immobilized aptamer on the indium thin oxide-coated surface was specifically bound to the H1 subtype only, which was consistent with the ELISA and FE-SEM results. Further measurement of CV using various amounts of H1 subtype provided the detection limit of the immobilized aptamer, which showed that a nanomolar scale of target protein was sufficient to produce the signal. These results indicated that the selected aptamer can be an effective probe for distinguishing the subtypes of influenza viruses by monitoring current changes.