• Bulletin of the Korean Chemical Society
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• 제25권4호
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• pp.539-544
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• 2004

The ability of protoberberine alkaloids, berberine and berberrubine, to act as topoisomerase II poisons is linked to the anti-cancer activity. Minor alterations in structure have a significant effect on their relative activity. Berberine, which has methoxy group at the 19-position, is significantly less potent than berberrubine. Several observations support non-specific binding to HP14 by the berberine: (i) nonspecific upfield changes in $^1H$ chemical shift for protons of the berberine; (ii) the broadening of imino protons of HP14 upon binding of the berberine; (iii) very small increases in duplex melting temperature in the presence of the berberine. Our results reveal that substitution of a hydroxyl group to a methoxy group on the 19-position, thereby converting the berberrubine to the berberine is associated with a non-specific DNA binding affinity and a reduced topoisomerase II poisoning. The presence of a bulky 19-methoxy substituent decreases intercalating properties of berberine and makes it inactive as topoisomerase II poison.

• BMB Reports
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• 제35권5호
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• pp.498-507
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• 2002

A gene that encodes a thermostable protease, coined thermicin, has been isolated from Thermoanaerobacter yonseiensis that is expressed and characterized in E. coli.. In order to elucidate the molecular characteristics on thermostability of the enzyme, molecular modeling and mutagenesis technology were applied. In the modeling structure, the structural core, including the active site, was well conserved; whereas, the two loop regions were unique when compared to thermitase. The mutant enzyme with the small loop deleted (D190-I196), based on modeling structural information, showed identical enzyme activity. However, when the large loop was deleted (P233-P244), a little lower $K_m$ and even a lower kcat was found. This indicates that the large loop could influence catalytic activity. However, the unfolding temperature ($T_m$), which was determined by a differential-scanning calorimetry for the mutant enzyme deleted the small loop, was $96^{\circ}C$. This is $14^{\circ}C$ lower than that for the parent thermicin. These results suggest that the small loop may play a role in maintaining the proper folding of the enzyme at high temperatures, whereas the large loop might be related to catalysis.

• 한국자기공명학회:학술대회논문집
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• 한국자기공명학회 2002년도 International Symposium on Magnetic Resonance
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• pp.90-90
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• 2002

Syndecans, transmembrane heparan sulfate proteoglycans, are coreceptors with integrin in cell adhesion process. It forms a ternary signaling complex with protein kinase C and phosphatidylinositol 4,5 bisphosphate (PIP2) for integrin signaling. NMR data indicates that cytoplasmic domain of syndecan-4 (4L) undergoes a conformational transition in the presence of PIP2, forming oligomeric conformation. The structure based on NMR data demonstrated that syndecan-4L itself forms a compact intertwined symmetric dimer with an unusual clamp shape for residues Leu$^{186}$ -Ala$^{195}$ . The molecular surface of the syndecan-4L dimer is highly positively charged. In addition, no inter-subunit NOEs in membrane proximal amino acid resides (Cl region) has been observed, demonstrating that the Cl region is mostly unstructured in syndecan-4L dimmer. However, the complex structure in the presence of PIP2 induced a high order multimeric conformation in solution. In addition, phosphorylation of cytoplasmic domain induces conformational change of syndecan-4, resulting inhibition of PKC signaling. The NMR structural data strongly suggest that PIP2 promotes oligomerization of syndecan-4 cytoplasmic domain for PKC activation and further induces structural reorganization of syndecan for mediating signaling network in cell adhesion procedure.

• BMB Reports
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• 제37권1호
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• pp.45-52
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• 2004

The goal of interaction proteomics that studies the protein-protein interactions of all expressed proteins is to understand biological processes that are strictly regulated by these interactions. The availability of entire genome sequences of many organisms and high-throughput analysis tools has led scientists to study the entire proteome (Pandey and Mann, 2000). There are various high-throughput methods for detecting protein interactions such as yeast two-hybrid approach and mass spectrometry to produce vast amounts of data that can be utilized to decipher protein functions in complicated biological networks. In this review, we discuss recent developments in analytical methods for large-scale protein interactions and the future direction of interaction proteomics.

• The Journal of the Acoustical Society of Korea
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• 제21권3E호
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• pp.126-131
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• 2002

Ultrasonic measurements are made in egg white to study the properties of the solution of the natural protein. The high-Q ultrasonic resonator method is used to get the ultrasonic absorption spectra over the range 0.2-10 ㎒ at 20℃. It is proportional to the 1.25th power of the frequency. The gelation process caused by heat is studied from the change in the velocity and the absorption. at 3 ㎒ using the pulse echo overlap technique over the range of 10-80℃. The absorption decreases with increasing temperature up to 60℃ where it turns up sharply and rapidly increases thereafter. The strong absorption in the gel region is described by the interaction between the solution and the network structure made of protein. Very slow variation in time elapse is observed after the temperature is quickly raised. It would be a real-time observation of the network building process and the characteristic time for the process is shown to be 400 min. A hysteresis phenomenon with respect to the temperature is observed. This phenomenon is associated with the memorizing effect of the network structure of protein of the gel.

• BMB Reports
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• 제50권9호
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• pp.478-483
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• 2017

Budding yeast has dozens of prions, which are mutually dependent on each other for the de novo prion formation. In addition to the interactions among prions, transmissions of prions are strictly dependent on two chaperone systems: the Hsp104 and the Hsp70/Hsp40 (J-protein) systems, both of which cooperatively remodel the prion aggregates to ensure the multiplication of prion entities. Since it has been postulated that prions and the remodeling factors constitute complex networks in cells, a quantitative approach to describe the interactions in live cells would be required. Here, the researchers applied dual-color fluorescence cross-correlation spectroscopy to investigate the molecular network of interaction in single live cells. The findings demonstrate that yeast prions and remodeling factors constitute a network through heterogeneous protein-protein interactions.

• 한국컴퓨터정보학회논문지
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• 제20권2호
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• pp.137-147
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• 2015

본 논문에서는 유전자 네트워크를 기반으로 유방암 환자의 예후를 예측하는 알고리듬을 제안한다. 유방암 환자의 마이크로어레이 데이터와 PPI(Protein-protein interaction)데이터를 이용하여 알고리듬의 분류자로 사용될 예후 특이 네트워크(Prognosis specific gene network)를 추출한다. PPI에 속한 모든 유전자 네트워크에 대하여 각각의 네트워크가 예후 좋음과 나쁨을 잘 구분하는지에 대한 점수를 피어슨 상관계수(Pearson's correlation coefficient)와 마이크로어레이 데이터를 이용하여 계산한다. 이들 중 가장 예후에 유의한 네트워크를 식별하고, 이 네트워크를 분류자로 사용하여 에스트로겐 수용체 음성 유방암 환자의 예후를 분류 분석 한다. 본 연구와 기존 연구의 알고리듬 정확도를 비교 분석 하기 위하여 독립 실험을 진행하고, 본 연구에서 제안된 알고리듬의 성능이 더 우수함을 보인다. 또한, Gene Ontology 데이터베이스를 활용하여 식별된 예후 특이 네트워크를 기능적으로 검증 한다.

• BMB Reports
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• 제34권1호
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• pp.33-38
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• 2001

The human PTK6 (also known as Brk) polypeptide, which is deduced from its full-length cDNA, represents a non-receptor protein tyrosine kinase (PTK). It contains SH3, SH2, and tyrosine kinase catalytic domains that are closely related to Src family members. We generated an antihuman PTK6 antibody by immunizing rabbits with a PTK6-specific oligopeptide conjugated to BSA, which corresponds to 11 amino acid residues near the C-terminus. An immunoblot analysis with the antibody detected an expected 52-kDa band in various mammalian transformed cell lines. Immunoprecipitation and immunoblot analyses demonstrated that PTK6 is phosphorylated on the tyrosine residues) and interacts with approximately a 23-kDa tyrosine-phosphorylated polypeptide (most likely a substrate of PTK6) in breast carcinoma T-47D cells. An immunofluorescence analysis demonstrated that PTK6 is localized throughout the cytoplasm of T-47D cells. These results support a possible role for PTK6 in the intracellular signal transduction through tyrosine phosphorylation.

• 한국정보통신학회논문지
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• 제20권9호
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• pp.1816-1821
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• 2016

단백질은 대부분의 생물학적 과정에서 중대한 역할을 수행하고 있으므로, 단백질 진화, 구조와 기능을 알아내기 위하여 많은 연구가 수행되고 있는데, 단백질의 이차 구조는 이러한 연구의 중요한 기본적 정보이다. 본 연구는 대규모 단백질 구조 자료로부터 단백질 이차 구조 정보를 효과적으로 추출하여 미지의 단백질 서열이 가지는 이차 구조를 예측하려 한다. 질의 서열과 상동관계에 있는 단백질 구조자료내의 서열들을 광범위하게 찾아내기 위하여, 탐색에 사용하는 프로파일의 구성에 질의 서열과 유사한 서열들을 사용하고 갭을 허용하여 반복적인 탐색이 가능한 PSI-BLAST를 사용하였다. 상동 단백질들의 이차구조는 질의 서열과의 상동 관계의 강도에 따라 가중되어 이차 구조 예측에 기여되었다. 이차 구조를 각각 세 개와 여덟 개로 분류하는 예측 실험에서 상동 서열들과 신경망을 동시에 사용하여 93.28%와 88.79%의 정확도를 얻어서 기존 방법보다 성능이 향상되었다.

• 한국정보과학회논문지:소프트웨어및응용
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• 제31권12호
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• pp.1602-1610
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• 2004

다양한 유전체 프로젝트로 말미암아 엄청난 서열 데이타들이 쏟아지고, 이에 따라 핵산 및 단백질 수준의 서열 데이타 분석이 매우 중요하게 인식되고 있다. 특히 최근에는 단백질이 단순하게 개별적인 기능을 가진 독립적인 요소가 아닌 전체 단백질 상호작용 네트워크 상에서 다른 객체들과 유기적인 관계를 갖으며 나름대로의 중요한 역할을 수행하고 있다는 점에 초점을 맞추어 연구가 진행되고 있다. 특히 단백질 상호작용 관계 분석을 위해서는 실제로 상호작용이 일어나는 도메인 모듈 정보가 아주 중요하게 작용하는데, 본 논문에서는 이러한 점을 고려하여 우리가 개발한 단백질 기능 및 상호작용 분석을 위한 PIVS(Protein-protein interaction Inference and Visualization System)에 대해 소개하고 있다 PIVS는 기존의 단백질 상호작용 데이타베이스들을 합쳐서 통합 데이타베이스를 생성하고, 다양한 전처리 과정으로 통합 데이타베이스 서열의 기능 및 주석 정보를 추출하여 로컬 데이타베이스화 하였다. 그리고 특히 단백질 상호작용 관계 분석을 위해 중요하게 작용하는 도메인 모듈 정보들을 추출하여 로컬 데이터베이스를 구축하였고, 기존의 단백질 상호작용 관계 데이타를 이용하석 도메인 사이의 상호작용 관계 정보도 수집하여 분석하였다. PIVS는 단백질의 종합적인 분석 정보, 즉, 기능 및 주석, 도메인, 상호작용 관계 정보 등을 손쉽고 편리하게 얻고자 하는 사용자에게 매우 유용하게 사용될 수 있을 것이다.