• BMB Reports
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• 제39권3호
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• pp.319-328
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• 2006

SecA protein, a cytoplasmic ATPase, plays a central role in the secretion of signal peptide-containing proteins. Here, we examined effects of signal peptide and ATP on the oligomerization, conformational change, and membrane binding of SecA. The wild-type (WT) signal peptide from the ribose-binding protein inhibited ATP binding to soluble SecA and stimulated release of ATP already bound to the protein. The signal peptide enhanced the oligomerization of soluble SecA, while ATP induced dissociation of SecA oligomer. Analysis of SecA unfolding with urea or heat revealed that the WT signal peptide induces an open conformation of soluble SecA, while ATP increased the compactness of SecA. We further obtained evidences that the signal peptide-induced oligomerization and the formation of open structure enhance the membrane binding of SecA, whereas ATP inhibits the interaction of soluble SecA with membranes. On the other hand, the complex of membrane-bound SecA and signal peptide was shown to resume nucleotide-binding activity. From these results, we propose that the translocation components affect the degree of oligomerization of soluble SecA, thereby modulating the membrane binding of SecA in early translocation pathway. A possible sequential interaction of SecA with signal peptide, ATP, and cytoplasmic membrane is discussed.

• Journal of Microbiology and Biotechnology
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• 제19권12호
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• pp.1582-1589
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• 2009

Bacterial UDP-N-acetylglucosamine enolpyruvyl transferase (MurA) catalyzes the transfer of enolpyruvate from phosphoenolpyruvate (PEP) to uridine diphospho-N-acetylglucosamine (UNAG), which is the first step of bacterial cell wall synthesis. We identified thimerosal, thiram, and ebselen as effective inhibitors of Haemophilus influenzae MurA by screening a chemical library that consisted of a wide range of bioactive compounds. When MurA was preincubated with these inhibitors, their 50% inhibitory concentrations ($IC_{50}s$) were found to range from 0.1 to $0.7\;{\mu}M$. In particular, thimerosal suppressed the growth of several different Gram-negative bacteria such as Escherichia coli, Pseudomonas aeruginosa, and Salmonella typhimurium at a concentration range of $1-2\;{\mu}g/ml$. These inhibitors covalently modified the cysteine residue near the active site of MurA. This modification changed the open conformation of MurA to a more closed configuration, which may have prevented the necessary conformational change from occurring during the enzyme reaction.

• 한국자기공명학회논문지
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• 제5권1호
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• pp.46-55
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• 2001

P23, a translationally controlled turner protein is involved in the interleukin-4 secretion from human basophils and is also known to be an IgE-dependent histamine-releasing factor. However, the precise physiological function and structure of P23 have not been elucidated. In the current study, we constructed the optimal expression and purification protocol of P23 and investigated the secondary structure and structural stability in various conditions. Circular dichroism (CD) investigation showed that the secondary structure of P23 adopts mainly a P-sheet conformation. CD spectroscopy and differential scanning calorimetry revealed that P23 is fairly stable in the pH range of neutral and mild-basic conditions and in the temperature range of 10 - 50$\^{C}$. Since the thermal stability and the P-sheet content of P23 were decreased by the addition of Ca$\^$2+/ ion, it could be suggested that Ca$\^$2+/ion induces structural change by partially destabilizing the structure of P23. In addition various H experiments were monitored to solve the aggregation of P23. Den results will provide the preliminary structural information about P23.

• 대한화학회지
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• 제31권5호
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• pp.471-475
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• 1987

수용액에서 Fe(II)-poly(D-glutamic acid) (PGA) 복합물 형성이 pH와 농도에 따라서 흡수와 원이색성 분광 광도계로 확인되었으며, 철 이온과 복합물 형성에 의한 PGA의 구조 변화와 안정도 상수도 검토되었다. PGA와 Fe(II)사이에 형성된 후 pH4.3에서는 ${\alpha}$-helix를 파괴(${\alpha}$-helix 파괴 효과)하고 pH5.7에서는 ${\alpha}$-helix를 유도(${\alpha}$-helix유도 효과)하는 것을 알 수 있었다. ${\alpha}$-helix의 PGA구조가 random coil의 PGA구조 보다 전 안정도 상수 값이 큰 것으로 보아 random coil의 PGA구조에서 더욱 안정된 복합물을 형성하고 있음을 알 수 있었다.

• Applied Microscopy
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• 제17권1호
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• pp.29-46
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• 1987

To study hexavalent chromium effects on mitochondrial electron transport, the activities of electron transport enzymes and conformational change of mitochondria treated with $40{\mu}M$ of sodium dichromate ($Na_{2}Cr_{2}O_{7}\;2H_{2}O$) were investigated. And so were those of liver mitochondria isolated from mouse intraperitoneally injected with sodium dichromate, 40mg per kg body weight. On both treatment with chromium(VI), the activities of electron transfer enzymes (Complex I and IV) were increased to some extent and the ultrastructural transformation of mitochondria from a condensed to an orthodox conformation was inhibited under State IV respiration. These results represent' inhibitory effect of hexavalent chromium on electron transport without inhibiting electron transfer enzymes (Complex I and IV) in mitochondria. On intraperitoneal treatment with hexavalent chromium as sodium dichromate and trivalent chromium as chromic chloride, containing 37.5 mg of chromium per kg body weight, respectively, the activities of electron transfer enzymes of liver isolated from mouse with chromium(VI) was reduced, but that with chromium(III) was not affected. And with chromium(VI), all mice after 12 hours of treatment died, only after 6 hours survived. With chromium(III), however, all survived. This indicates that hexavalent chromium is more toxic than trivalent chromiumin mouse liver.

• 한국자기공명학회논문지
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• 제19권3호
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• pp.149-155
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• 2015

Acyl carrier protein is related with fatty acid biosynthesis in which specific enzymes are involved. Especially, acyl carrier protein (ACP) is the key component in the growing of fatty acid chain. ACP is the small, very acidic protein that covalently binds various intermediates of fatty acyl chain. Acylation of ACP is mediated by holo-acyl carrier protein synthase (ACPS), which transfers the 4'PP-moiety of CoA to the 36th residue Ser of apo ACP. Acyl carrier protein P (ACPP) is one of ACPs from Helicobacter plyori. The NMR structure of ACPP consists of four helices, which were reported previously. Here we show how acylation of ACPP can affect the overall structure of ACPP and figured out the contact surface of ACPP to acyl chain attached during expression of ACPP in E. coli. Based on the chemical shift perturbation data, the acylation of ACCP seems to affect the conformation of the long loop connecting helix I and helix II as well as the second short loop connecting helix II and helix III. The significant chemical shift change of Ile 54 upon acylation supports the contact of acyl chain and the second loop.

• 대한수의학회지
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• 제53권3호
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• pp.155-158
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• 2013

Paedomorphosis is the retention of juvenile morphology at maturity and is important in generating evolutionary change in domestic species and species in the wild. This preliminary study compared morphological characteristics of seven domestic cat pure breeds and felid species from around the world. An original procedure based on elliptical Fourier (EF) methods was applied to head lateral views of specimens and were assessed in order to analyse head profile. For comparative purposes three domestic kittens of different ages and three species of genus Lynx were also used. EF descriptors, allowed for the quantification of the head profile. Using the Fourier transform, reconstruction of the mean head profile revealed that there was a general shape difference between wild cats, domestic cats and kittens. Results suggested that variability in head profile differentiate quite well between adult cats and kittens, but domestic and wild cats appeared grouped into a similar cluster. The similarity between breeds can thus be attributed more to the general head profile than to flatness, i.e. to the general conformation rather than facial profile. Therefore, no effect of paedomorphism on the studied breeds can be undertaken. The present approach opens interesting ethnological perspectives for the aloidic characterisation for domestic breeds.

• Bulletin of the Korean Chemical Society
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• 제28권5호
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• pp.772-776
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• 2007

In order to study the role of residue in the active site of glutathione S-transferase (GST), Arg13 residue in human GST P1-1 was replaced with alanine, lysine and leucine by site-directed mutagenesis to obtain mutants R13A, R13K and R13L. These three mutant enzymes were expressed in Escherichia coli and purified to electrophoretic homogeneity by affinity chromatography on immobilized GSH. Mutation of Arg13 into Ala caused a substantial reduction of the specific activity by 10-fold. Km GSH, Km DCNB and Km EPNP values of R13A were approximately 2-3 fold larger than those of the wild type. Mutation of Arg13 into Ala also significantly affected I50 values of S-methyl-GSH that compete with GSH and ethacrynic acid, an electrophilic substrate-like compound. These results appeared that the substitution of Arg13 with Ala resulted in significant structural change of the active site. Mutation of Arg13 into Leu reduced the catalytic activity by approximately 2-fold, whereas substitution by Lys scarcely affected the activity, indicating the significance of a positively charged residue at position 13. Therefore, arginine 13 participates in catalytic activity as mainly involved in the construction of the proper electrostatic field and conformation of the active site in human GST P1-1.

• Bulletin of the Korean Chemical Society
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• 제10권1호
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• pp.107-111
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• 1989

Glucoamylase was inactivated with 1-ethyl-2-(dimethylaminopropyl)carbodiimide (EDC) at pH 5.0. Time course of inactivation of glucoamylase was at least biphasic. From the results of the titration of SH groups with Ellman's reagent and hydroxylamine treatment at pH 7.0, it was concluded that the crucial sites of modification were carboxyl groups of glucoamylase. The CD spectrum of EDC-modified glucoamylase suggested that the gross conformation of the native enzyme was retained. The inactivation of glucoamylase was reduced remarkably in the presence of maltose. The logarithm of the half-life of the inactivation of glucoamylase by EDC was a linear function of log[EDC] in each stage indicating that one carboxyl group among the modified ones was crucial for inactivation of glucoamylase. The change in the binding affinity due to modification was determined by using an affinity column. It indicates that the carboxyl group of glucoamylase seems to play a role in both, the catalysis and substrate binding in the first stage, but in the second stage the binding affinity is recovered almost up to that of native enzyme.

• Bulletin of the Korean Chemical Society
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• 제15권2호
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• pp.161-167
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• 1994

Rate constants have been measured spectrophotometrically for the nucleophilic substitution reactions of aryl substituted benzenesulfonates (3) with alkali metal ethoxides ($EtO^-M^+$) and butane-2,3-dione monoximates ($Ox^-M^+$) in ethanol at $25^{\circ}C$. The reactivity of the alkali metal ethoxides decreases in the order $EtO^-K^+> EtO^- > EtO^-Li^+$, indicating that $K^+$ ion behaves as a catalyst and $Li^+$ ion acts as an inhibitor for all the substrates studied. For the corresponding reactions of 3 with Ox^-M^+$, $Li^+$ ion also exhibits inhibitory effect for all the substrates, while, $K^+$ ion shows catalytic or inhibitory effects depending on the nature of substituents on the acyl and phenyl moieties. A study of substituent effect on rate has revealed that both EtO^- $and Ox^-$ systems have the same reaction mechanism. The different behavior shown by $K^+$ ion for the reaction of 3 with $EtO^-$ and $Ox^-$ would be attributed to a difference in charge polarization of S=O bond in the transition state between the two systems and/or a change in conformation of Ox^-K^+$.