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Pratap Karki,Eunsook Lee,Michael Aschner 대한직업환경의학회 2013 대한직업환경의학회지 Vol.25 No.-
Manganese (Mn) is an essential element that is required in trace amount for normal growth, development as well maintenance of proper function and regulation of numerous cellular and biochemical reactions. Yet, excessive Mn brain accumulation upon chronic exposure to occupational or environmental sources of this metal may lead to a neurodegenerative disorder known as manganism, which shares similar symptoms with idiopathic Parkinson’s disease (PD). In recent years, Mn exposure has gained public health interest for two primary reasons: continuous increased usage of Mn in various industries, and experimental findings on its toxicity, linking it to a number of neurological disorders. Since the first report on manganism nearly two centuries ago, there have been substantial advances in the understanding of mechanisms associated with Mn-induced neurotoxicity. This review will briefly highlight various aspects of Mn neurotoxicity with a focus on the role of astrocytic glutamate transporters in triggering its pathophysiology.
Construction of Covalently Linked Caspase-9 Dimer and Its Biochemical Characterization
Karki, Pratap,Dahal, Giri Raj,Park, Il-Seon 朝鮮大學校 附設 醫學硏究所 2007 The Medical Journal of Chosun University Vol.32 No.1
The activation of caspase-9 is best described by induced proximity model that postulates the dimer-driven assembly of monomeric caspase-9 in apoptosome as an activation mechanism. Further, the crystallographic structure of active caspase-9 has shown that termini of monomers lie quite close to each other. With an aim to analyze the role of dimehzation and proteolytic processing in activation, constitutively dimeric forms of caspase-9 were engineered by connecting termini of two caspase-9 molecules. These dimers could be overexpressed and purified in Escherichia coli. The recombinant dimers showed 2-fold increment in specific activity over their respective monomer that was lower than expected if dimerization is the only mechanisJi to activate caspase-9. Citrate, a well-known kosmotrope to enhance dimenzation, increased the activity of wild type monomer and dimer by -75 and -10 times respectively which was -5 times better than that of corresponding uncleavable mutant ones. The possible reason behind this failure of engineered dimers to mimic Apaf-l activated caspase-9 may lie in the distinctly different scenario of dimehzation in two cases or it may be the outcome of the defective design that restricted the complete dimehzation. However, this simple design could enable to produce constitutively dimeric caspase-9 with catalytic advancements over their monomers that may be helpful for future studies to elucidate the molecular mechanism of caspase-9 activation.
Thapa, Arjun,Shahnawaz, Md,Karki, Pratap,Raj Dahal, Giri,Sharoar, Md Golam,Yub Shin, Song,Sup Lee, Jung,Cho, Byungyun,Park, Il-Seon Eaton Pub. Co 2008 Biotechniques Vol.44 No.6
<P>Proteins and peptides expressed in the prokaryotic system often form inclusion bodies. Solubilization and refolding procedures can be used for their recovery, but this process remains difficult. One strategy for improving the solubility of a protein of interest is to fuse it to a highly soluble protein. To select a suitable fusion partner capable of solubilizing the aggregation-prone (inclusion body-forming) proteins and peptides, Escherichia coli thermostable proteins were identified and tested. Among them, trigger factor (TF) protein was selected because of its high expression and stability. Using an expression system based on fusion to TF, selected proteins and peptides that otherwise form inclusion bodies were expressed in soluble state and were purified like other soluble proteins. This system provides a convenient method for production of aggregation-prone proteins and peptides.</P>