• Journal of Life Science
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• v.6 no.3
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• pp.213-218
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• 1996

Symbionin, ahomologue of E. coli GroEL, produced by an intracellular symbiont of the pea aphid , has molecular chaperone activity bothin vitro and in vivo, and it is able to tarnsfer its high-energy phospholy group to other compounds through its autophosphorylation and phosphotransferase activity. The symbionin is a novel histidine protein Kinase and a senor molecular of the two-component pathway.

• BMB Reports
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• v.43 no.3
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• pp.170-175
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• 2010

Chaperone;Glutathione peroxidase;Peroxiredoxin;Schizosaccharomyces pombe;Thioredoxin peroxidase;To investigate the differences in the functional roles of peroxiredoxins (Prxs) and glutathione peroxidase (GPx) of Schizosaccharomyces pombe, we examined the peroxidase and molecular chaperone properties of the recombinant proteins. TPx (thioredoxin peroxidase) exhibited a capacity for peroxide reduction with the thioredoxin system. GPx also showed thioreoxin-dependent peroxidase activity rather than GPx activity. The peroxidase activity of BCP (bacterioferritin comigratory protein) was similar to that of TPx. However, peroxidase activity was not observed for PMP20 (peroxisomal membrane protein 20). TPx, PMP20, and GPx inhibited thermal aggregation of citrate synthase at 43$^{\circ}C$, but BCP failed to inhibit the aggregation. The chaperone activities of PMP20 and GPx were weaker than that of TPx. The peroxidase and chaperone properties of TPx, BCP, and GPx of the fission yeast are similar to those of Saccharomyces cerevisiae. The fission yeast PMP20 without thioredoxin-dependent peroxidase activity may act as a molecular chaperone.

• BMB Reports
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• v.42 no.10
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• pp.623-630
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• 2009

Hsp90, an evolutionarily conserved molecular chaperone, is involved in the folding, stabilization, activation, and assembly of a wide range of 'client' proteins, thus playing a central role in many biological processes. Especially, several oncoproteins act as Hsp90 client proteins and tumor cells require higher Hsp90 activity than normal cells to maintain their malignancy. For this reason, Hsp90 has emerged as a promising target for anti-cancer drug development. It is still largely unknown how Hsp90 can recognize structurally unrelated client proteins. However, recent progress in structural studies on Hsp90 and its interaction with various co-chaperones has broadened our knowledge of how the Hsp90 ATPase activity, which is essential for its chaperone function, is regulated and coupled with the conformational changes of Hsp90 dimer. This review focuses on the roles of various Hsp90 co-chaperones in the regulation of the Hsp90 ATPase cycle, as well as in the selection of client proteins. In addition, the current development of Hsp90 inhibitors based on the structural information will be discussed.

• BMB Reports
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• v.42 no.11
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• pp.713-718
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• 2009

Apoptotic DNA fragmentation, the hallmark of apoptosis, is mediated primarily by caspase-activated DFF40 (CAD) nuclease. DFF40 exists as a heterodimer with DFF45 (ICAD), which is a specific chaperone and inhibitor of DFF40 under normal conditions. To understand the mechanism through which the DFF40/DFF45 system is regulated, we analyzed the structural and biochemical properties of apoptotic DNA fragmentation mediated by DFF40/DFF45. Using limited proteolysis, we show that residues 1-281 of DFF45 form a rigid, crystallized domain, whereas the loop formed by residues 277-281 is accessible by trypsin. These results show that the C-terminal helix formed by residues 281-300 is dynamic and necessary for the chaperone activity of DFF45, but not for inhibition of DFF40.

• BMB Reports
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• v.50 no.5
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• pp.235-236
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• 2017

The circadian clock is an internal system that is synchronized by external stimuli, such as light and temperature, and influences various physiological and developmental processes in living organisms. In the model plant Arabidopsis, transcriptional, translational and post-translational processes are interlocked by feedback loops among morning- and evening-phased genes. In a post-translational loop, plant-specific single-gene encoded GIGANTEA (GI) stabilize the F-box protein ZEITLUPE (ZTL), driving the targeted-proteasomal degradation of TIMING OF CAB EXPRESSION 1 (TOC1) and PSEUDO-RESPONSE REGULATOR 5 (PRR5). Inherent to this, we demonstrate the novel biochemical function of GI as a chaperone and/or co-chaperone of Heat-Shock Protein 90 (HSP90). GI prevents ZTL degradation as a chaperone and facilitates ZTL maturation together with HSP90/HSP70, enhancing ZTL activity in vitro and in planta. GI is known to be involved in a wide range of physiology and development as well as abiotic stress responses in plants, but it could also interact with diverse client proteins to increase protein maturation. Our results provide evidence that GI helps proteostasis of ZTL by acting as a chaperone and a co-chaperone of HSP90 for proper functioning of the Arabidopsis circadian clock.

• BMB Reports
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• v.42 no.12
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• pp.812-816
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• 2009

To screen chaperone proteins from Schizosaccharomyce pombe (S. pombe), we prepared recombinant citrate synthase of the fission yeast as a substrate of anti-aggregation assay. Purified recombinant citrate synthase showed citrate synthase activity and was suitable for the substrate of chaperone assay. Several heat stable proteins including aspartyl aminopeptidase (AAP) for candidates of chaperone were screened from the supernatant fraction of heat-treated crude extract of S. pombe. The purified AAP migrated as a single band of 47 kDa on SDS-polyacrylamide gel electrophoresis. The native size of AAP was estimated as 200 kDa by a HPLC gel permeation chromatography. This enzyme can remove the aspartyl residue at N-terminus of angiotensin I. In addition, AAP showed the heat stability and protected the aggregation of citrate synthase caused by thermal denaturation. This study showed that S. pombe AAP is a moonlight protein that has aspartyl aminopeptidase and chaperone activities.

• Archives of Pharmacal Research
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• v.27 no.3
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• pp.319-323
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• 2004

Cytochrome P450 (CYP) 3A4 is of great interest because of its important roles in the oxidation of numerous drugs and xenobiotics. HDJ-1, a molecular chaperone in human, is known to assist the correct folding of unfolded proteins. To achieve a high yield of recombinant human CYP3A4 in Escherichia coli, the CYP3A4 encoding gene was co-expressed with the chaperone HDJ-1, under the control of an inducible tac promoter in a bicistronic format. The levels of expression of the CYP3A4 in the bicistronic construct reached up to 715 nmol $(liter culture)^{-1}$ within 16 h at $37^{\circ}C$, which was about a 3.3-fold increase compared to that of the CYP3A4 alone without the HDJ-1. By co-expression with HDJ-1, the catalytic activity of CYP3A4 was also increased by -15-fold. The amount of activity increase was similar to that of the CYP production at the whole cell level. The present over-expression system may be useful for the rapid production of large amounts of active CYP3A4 in E. coli.

• Journal of Microbiology and Biotechnology
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• v.12 no.6
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• pp.1002-1005
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• 2002

The effects of GroEL/ES chaperone on the production of soluble form of B. macerans cyclodextrin glucanotransferase (CGTase) in recombinant E. coli were investigated. The cgt gene and groEL/ES genes are under the control of T7 promoter and Pzt-1 promoter, respectively. The optimal concentrations of inducers, IPTG and tetracycline, were found to be 1.0 mM and 10 ng/ml, respectively. When tetracycline and IPTG were added at the early exponential phase (2h) and exponential phase (3h) of growth, respectively, about 1.5-fold increase of soluble CGTase activity and 1.6-fold increase of soluble CGTase protein were obtained. An SDS-PAGE analysis revealed that about $37.2\%$ of total CGTase protein was in the soluble fraction when GroEL/ES chaperone was overexpressed.

• Molecules and Cells
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• v.20 no.2
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• pp.173-182
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• 2005

Heat shock protein gp96 is an endoplasmic reticulum chaperone, belonging to the HSP90 family. The function of gp96 as a molecular chaperone was discovered more than 10 years ago, but its importance has been overshadowed by the brilliance of its role in immune responses. It is now clear that gp96 is instrumental in the initiation of both the innate and adaptive immunity. Recently, the roles of gp96 in protein homeostasis, as well as in cell differentiation and development, are beginning to draw more attention due to rapid development in the structural study of HSP90 and some surprising new discoveries from genetic studies of gp96. In this review, we focus on the aspect of gp96 as an ER molecular chaperone in protein maturation, peptide binding and the regulation of its activity.

• Molecules and Cells
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• v.38 no.2
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• pp.187-194
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• 2015

Thioredoxin (TRX) is a disulfide reductase present ubiquitously in all taxa and plays an important role as a regulator of cellular redox state. Recently, a redox-independent, chaperone function has also been reported for some thioredoxins. We previously identified nodulin-35, the subunit of soybean uricase, as an interacting target of a cytosolic soybean thioredoxin, GmTRX. Here we report the further characterization of the interaction, which turns out to be independent of the disulfide reductase function and results in the co-localization of GmTRX and nodulin-35 in peroxisomes, suggesting a possible function of GmTRX in peroxisomes. In addition, the chaperone function of GmTRX was demonstrated in in vitro molecular chaperone activity assays including the thermal denaturation assay and malate dehydrogenase aggregation assay. Our results demonstrate that the target of GmTRX is not only confined to the nodulin-35, but many other peroxisomal proteins, including catalase (AtCAT), transthyretin-like protein 1 (AtTTL1), and acyl-coenzyme A oxidase 4 (AtACX4), also interact with the GmTRX. Together with an increased uricase activity of nodulin-35 and reduced ROS accumulation observed in the presence of GmTRX in our results, especially under heat shock and oxidative stress conditions, it appears that GmTRX represents a novel thioredoxin that is co-localized to the peroxisomes, possibly providing functional integrity to peroxisomal proteins.