• Journal of Life Science
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• v.34 no.4
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• pp.279-285
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• 2024

The zonula occludens (ZO) protein serves as a scaffolding protein, providing structural support at the junctions between cells and the cytoplasmic surface. It acts as a bridge between integral membrane proteins and the cytoskeleton. Besides its structural role, it also participates in regulating cell growth and proliferation. Recent studies have highlighted the involvement of ZO protein in various diseases, including cancer. Specifically, research has indicated that ZO protein influences the cancer microenvironment surrounding cancer cells, thereby facilitating their growth and development. ZO proteins exert diverse functions in the cancer microenvironment, impacting processes such as angiogenesis, inflammatory responses, the epithelial-mesenchymal transition, and interactions with mesenchymal stem cells. The specific mechanisms vary depending on the type of cancer and environmental conditions. Recent research unveiled several signaling pathways involving ZO protein, which could potentially impede cancer progression in the tumor microenvironment. Consequently, these insights open avenues for novel treatment strategies. While the numerous physiological, structural, and morphological roles of ZO protein have been observed at the cellular and in vivo levels, understanding the signaling mechanisms it operates in vivo and how these mechanisms influence the cancer microenvironment remains a challenge. In this review, we delineate the characteristics and regulatory mechanisms of ZO protein in the context of the cancer microenvironment. Additionally, we propose leveraging the properties of ZO protein to devise defense mechanisms within the cancer cell environment and provide an overview of its in vivo role.

• Korean Journal of Microbiology
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• v.31 no.4
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• pp.274-278
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• 1993

Overproduced proteins in many cases result in forming insoluble inclusion bodies, and their formation might be due to high concentration of protein. To investigate how proteins become insoluble, chloramphenicol acetyltransferase (CAT) and .betha.-lactamase were overproduced, and their solubilities and activities were determined. CAT was accumulated from 9 to 45% of total cellular protein in a fully soluble form without inclusion body formation. CAT specific activity was shown to be proportional to the amount of the protein produced. Moderately produced .betha.-lactamase by the phase T7 expression system at 30.deg.C comprised only mature forms in a soluble form. However, overproduced .betha.-lactamase at 37.deg.C became insoluble. Most precursor forms of .betha.-lactamase in the cytoplasm were insoluble, whereas majority of the mature forms in the periplasm space were soluble. Also, chaperone GroE proteins which assist proper protein folding and translocation did not increase .betha.-lactamase solubility significantly under the experimental condition. It seems that the formation of inclusion bodies in the cell is related to the nature of protein itself rather than just to high concentration of protein.

• Microbiology and Biotechnology Letters
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• v.47 no.4
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• pp.574-580
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• 2019

ATP drives the conformational change of the group II chaperonin from the open lid substrate-binding conformation to the closed lid conformation to encapsulate an unfolded protein in the central cavity. It is thought that the folding activity of group II chaperonin is strongly correlated with the ATP-dependent conformational change ability. In order to confirm the dependence of the reaction temperature and ATP concentration of PhCpn, the ATPase activities were measured under different reaction temperatures and ATP concentrations. The maximal ATPase activity of PhCpn was observed at 80℃ and 3 mM ATP concentration. As a result of ATPase activity according to the type of salt ions, the highest activity was observed at 300 mM LiCl among the univalent cations and 5 mM MgCl₂ among the divalent cations, respectively. The values of Km and Vmax for ATP substrate were estimated as 2.17 mM and 833.3 μM/min, respectively. This results provide the enzymatic information of PhCpn when the prolonged and high activities of pharmaceutical and industrial proteins (or enzymes), by using chaperonin molecules, are required.