• BMB Reports
• /
• v.32 no.1
• /
• pp.12-19
• /
• 1999

Gaegurin 4 (GGN4), a broad-spectrum antibiotic, is a 37-amino acid peptide isolated from the Korean frog, Rana rugosa. In this study, we have chemically synthesized and purified GGN4 analogues where the C-terminal portion is truncated and/or substituted with tryptophan. These peptides show significantly different biological activities depending on the location of tryptophan and the number of amino acids truncated from the C-terminal end. While deletion of 9 amino acids from the C-terminal seems to be marginally tolerable in maintaining the antimicrobial activity, further deletion of up to 14 amino acid residues decreases the potency by more than 60-fold towards Gram-positive, and 10-fold towards Gram-negative, bacteria. Surprisingly, the reduced activity of the shorter peptide can be completely restored by a single substitution of aspartic acid 16 to tryptophan 16 (D16W). Also, the truncation seems to decrease the specificity of antibiotic activity more towards Gram-positive than towards Gram-negative bacteria studied. These data suggest a partial role of the C-terminal region in determining the binding specificity and the activity of peptides upon binding to their target cell membranes.

• The Journal of Korean Society of Virology
• /
• v.30 no.1
• /
• pp.71-81
• /
• 2000

We have determined and analyzed the full-length cDNA sequence of a coxsackievirus B3 (CVB3) Korean isolate (CVB3-Korea/97) which has been known as a general human pathogen. The whole genome contains 7,400 nucleotides and has a single large open reading frame with 6,555 nucleotides that encodes a potential polyprotein precursor of 2,185 amino acids. The genome also contains a 5' non-coding region (NCR) of 741 bases and a 3' NCR of 104 bases followed by poly(A) tail. Sequence homologies of nucleotides and deduced amino acids between the CVB3-Korea/97 strain and the prototype (Nancy strain) were 81.7% and 91.5%, respectively. The genes encoding the functional proteins including viral protease and RNA dependent RNA polymerase showed higher homology than those encoding the structural proteins. We have further analyzed the sequences of 5' NCR, VP1 and VP2 of CVB3-Korea/97, which are known as cardiovirulent determining factors at the nucleotide and amino acid levels. Although the CVB 3-Korea/97 strain was isolated from an aseptic meningitis patient without cardiomyopathy, its 234th nucleotide and 165th amino acid were uracil and Asn as same as those of other cardiovirulent strains one. However, the 155th amino acid of VP1, which closely associated with cardiovirulence, was replaced with $Arg^{155}$ by single nucleotide substitution from $A^{2916}$ to $T^{2916}$. Moreover, additional amino acid substitutions were observed in the flanking region of $Asp^{155}$. Taken together, amino acid(s) substitution in VP1 may playa critical role in determining cardiovirulence of the CVB3-Korea/97 strain rather than individual nucleotide replacements in the 5' NCR and/or an amino acid substitution in VP2.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.3 no.1
• /
• pp.69-76
• /
• 1974

The method of amino acid sequence determination from the C-terminal amino acid is proposed and mass spectrometric identification of thiohydantoins described previously. In this paper was discussed the fragmentation of thiohydantoin-ring by deutero substitution and model tripeptide have been degraded through three stages each, with interpretable results. The conditions employed in this method are mild enough for biological materials. The main features of the method are the following. 1. Thiohydantoins were formed in a non-aqueous medium a mixture of acetic anhydride, acetic acid and ammonium thiocyanate. 2. Mass sepectra of thiohydantoins derived from 20 amino acids were obtained with a mass spectrometer, JEOL model JMS-06H. 3. Cleavage of peptidyl thiohydantoin was made with an acidic from of a cation-exchange resin. (Amberlite IR-120) 4. Separation of the cleaved thiohydantoin and the parent peptide less one amino acid moiety was made by chromatography on a Sephadex G-10 column. 5. The peptide fraction was concentrated by freezedrying. 6. Thiohydantoin derivative of carboxyl terminal amino acid residue was introduced with a direct inlet probe in methanol solution.

• Bulletin of the Korean Chemical Society
• /
• v.17 no.5
• /
• pp.428-432
• /
• 1996

Amino acid cobalt(Ⅲ) complexes of 1,3-diminopropane-N,N'-di-α-(β-methyl)-pentanoic acid (H2dpdmp), uns-cis-[Co(dpdmp)(aa)] (aa=glycine, S-alanine, R-aspartic acid, sarcosine) have been prepared from the reaction between the uns-cis-[Co(dpdmp)Cl2]- complex and the corresponding amino acid. In the reaction with the uns-cis-[Co(dpdmp)Cl2]- complex, glycine and S-alanine have yielded both merridional and facial isomers, while R-aspartic acid and sarcosine, only merridional isomers. The stereospecific substitution reaction of R-aspartic acid to racemic uns-cis-[Co(dpdmp)Cl2]- complex has yielded two merridional diastereomers; ΛR-uns-cis- and ΛR-uns-cis-[Co(dpdmp)(R-asp)]. It is of interest to note that this is one of the few CoⅢ(ONNO)(aa) type complex preparations, which gives only one isomer with stereospecificity. On the other hand, two merridional products obtained from the reaction of sarcosine with racemic uns-cis-[Co(dpdmp)Cl2]- are turned out to be mixtures of optical isomers.

• BMB Reports
• /
• v.31 no.3
• /
• pp.281-286
• /
• 1998

Hepatitis C virus (HCV) core proteins from two different isolates (HCV-1 and HCV-RH) were expressed in Spotioptera Jrugiperda (Sf9) insect cells. The RH core consisted of two major species of proteins (21 kDa and 19 kDa). On the other hand, the HCV-1 core was approximately 16 kDa in a SDS-PAGE gel. Both core proteins were phosphorylated in vivo on serine residues. Furthermore, the RH core but not HCV-1 core formed dimers, indicating that the protein conformation of the core in these two isolates is dfferent from one another. Immunofluorescence studies showed that the RH core was present in the cytoplasm, whereas the HCV-1 core was localized predominantly to the nucleus in recombinant baculovirus-infected insect cells. Since the major difference between the two isolates is the codon 9 of the core protein, a single amino acid substitution appears to play a major role in the protein conformation and these properties may reflect the different biological functions of core proteins in HCV-infected cells.

• Korean Journal of Microbiology
• /
• v.29 no.5
• /
• pp.278-283
• /
• 1991

Two amino acid residues ($Ala^{494}$ and $Ser^{495}$ of E. coli .gamma.-glutamylcysteine synthetase have been investigated whether they are the site of feedback inhibition by site specific mutagenesis. Single substitution of $serine^{495}$ (S495F), and double substitutions of alanine$^{494}$ and $serine^{495}$ (A494G-S495F) resulted in the inactivation of the .gamma.-glutamylcysteine synthetase activity. Substitution of $alanine^{494}$ with $glycine^{494}$ resulted in a higher level of feedback inhibition. These results suggest that $serine^{495}$ in .gamma.-glutamylcysteine synthetase is required for its catalytic acitvity and $alanine^{494}$ is presumably related to the feeback inhibition site.

• BMB Reports
• /
• v.28 no.4
• /
• pp.363-367
• /
• 1995

E. coli methionyl-tRNA synthetase is one of the class I tRNA synthetases. The Tryptophane residue at the position 461 located in the C-terminal domain of the enzyme is a key amino acid for the interaction with the anticodon of $tRNA^{Met}$. W461 was replaced with other amino acids to determine the chemical requirement for the interaction with the anticodon of $tRNA^{Met}$. Saturation mutagenesis at the position 461 generated a total of 12 substitution mutants of methionyl-tRNA synthetase. All the mutants showed the same in vivo stability as the wild-type enzyme, suggesting that the amino acid substitutions did not cause severe conformational change of the protein The mutants containing tyrosine, phenylalanine, histidine and cysteine substitutions showed in vivo activity while all the other mutants did not. The comparison of the in vitro aminoacylation activities of these mutants showed that aromatic ring structure, Van der Waals volume and hydrogen bond potential of the amino acid residue at the position 461 are the major determinants for the interaction with the anticodon of $tRNA^{Met}$.

• Bulletin of the Korean Chemical Society
• /
• v.20 no.10
• /
• pp.1126-1128
• /
• 1999

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.26 no.6
• /
• pp.1152-1158
• /
• 1997

In order to develop new soysauce using mountain edible herbs, cirsium setidens Nakai and comfrey were added to the raw material of soysauce as a partially substituting ingredient to wheat composing the total nitrogen. The changes of chemical composition of soysauce by the substitution of 1~5% cirsium setidens after four months of aging were similar to those of the control soysauce. On the other hand, total solid content was decreased, while the pH was increased by more than 7%. The total nitrogen and solid contents in the confrey substituted soysauce were increased with the increment of the amount of comfrey, but showed little changes of the pH. The mineral contents of calcium and potassium in the soysauce after four months of aging at 10% substitution of cirsium setidens were increased by 1.7 and 1.4 times, respectively. A significant increase in calcium(2.3 times as compared to the control) was also observed in 7% substitution of comfrey. The amino acid contents such as methionine, tyrosine and histidine were markedly increased at 3% substitution of cirsium setidens. With 5% substitution of comfrey, the contents of tyrosine, glutamic acid methionine were increased by 4.4, 1.8 and 1.7 times, respectively as compared to the control. The results of sensory evaluation revealed that overall acceptability of soysauce with 1~5% substitution of cirsium setidens and 5% of comfrey exceeded other samples composing different ratios of substituting ingredients.

• BMB Reports
• /
• v.32 no.5
• /
• pp.468-473
• /
• 1999

Nuclear Factor 1 (NF1) proteins are a family of transcriptional factors consisting of four different types: NF1-A, -B, -C, and -X. Some NF1 transcription factors contain a heptasequence motif, SPTSPSY, which is found as a repeat sequence in the carboxy terminal domain (CTD) of the largest subunit of RNA polymerase II. A similar heptasequence, SPTSPTY, is contained in rat liver NF1-A at a position between residues 469 and 475. In order to investigate the roles of the individual amino acids of the heptasequence of rat liver NF1-A in transcriptional activation, we systematically substituted single and multiple amino acid residues with alanine residue(s) and evaluated the transcriptional activities of the mutated NF1-A. Substitution of a single amino acid reduced transcriptional activity by 10 to 30%, except for the proline residue at position 473, whose substitution with alanine did not affect transcriptional activity. However, changes of all four serine and threonine residues to alanine or of the tyrosine residue along with the serine residue at position 469 to alanine reduced the activity to almost background levels. Our results indicate that multiple serine and threonine residues, rather than a single residue, may be involved in the modulation of the transcriptional activities of the factor. Involvement of the tyrosine residue is also implicated.