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Proteins Heading for the Chloroplast
Hong, Choo Bong 한국식물학회 1990 Journal of Plant Biology Vol.33 No.1
The chloroplast has been the prime light-energy harvesting organelle on earth. It also carries out several key metabolic processes, such as lipid synthesis and nitrogen metabolism. Even though the chloroplast has its own genome, its coding capacity can afford only dozens of proteins, and most of the proteins functioning in the chloroplast are imported from the cytosol where nuclear encoded chlorplast genes are synthesized on free cytosokic ribosomes. Precursor proteins synthesized on cytosolic ribosomes have transit peptides at the amino termini of the proteins, and the transit peptide is sufficient to transfer chloroplast proteins from the cytosol into the chloroplast. When comparing amino acid sequences duduced from the nucleotide sequences of the clones of the chloroplast proteins, high homologies can be found among the transit peptides of proteins with the same function. Overall amino acid compositions of the transit peptides show amphiphilic characters of the transit peptides, and the amphiphilicity indicates that three dimensional structure of the transit peptide is responsible for the translocation of the chloroplast proteins.
Biochemical Analysis of a Cytosolic Small Heat Shock Protein, NtHSP18.3, from Nicotiana tabacum
Choo Bong Hong,Ji Hee Yu,Keun Pill Kim,Soo Min Park 한국분자세포생물학회 2005 Molecules and cells Vol.19 No.3
Small heat shock proteins (sHSPs) are widely distributed,and their function and diversity of structure have been much studied in the field of molecular chaperones. In plants, which frequently have to cope with hostile environments, sHSPs are much more abundant and diverse than in other forms of life. In response to high temperature stress, sHSPs of more than twenty kinds can make up more than 1% of soluble plant proteins. We isolated a genomic clone, NtHSP18.3, from Nicotiana tabacum that encodes the complete open reading frame of a cytosolic class I small heat shock protein. To investigate the function of NtHSP18.3 in vitro, it was overproduced in Escherichia coli and purified. The purified NtHSP18.3 had typical molecular chaperone activity as it protected citrate synthase and luciferase from high temperature-induced aggregation. When E. coli celluar proteins were incubated with NtHSP18.3, a large proportion of the proteins remained soluble at temperatures as high as 70°C. Native gel analysis suggested that NtHSP18.3 is a dodecameric oligomer as the form present and showing molecular chaperone activity at the condition tested. Binding of bis-ANS to the oligomers of NtHSP18.3 indicated that exposure of their hydrophobic surfaces increased as the temperature was raised. Taken together, our data suggested that NtHSP18.3 is a molecular chaperone that functions as a dodecameric complex and possibly in a temperature-induced manner.
A Simple Procedure for RNA Isolation from Plants and Preservation of Plant Material for RNA Analysis
Hong, Choo-Bong,Jeon, Jae-Heung 한국식물학회 1987 Journal of Plant Biology Vol.30 No.3
Total RNA was isolated from two months old wheat, rice, tobacco and sweet potato. The procedure used was simple and provided pure RNA preparation. Lysis of plant tissue in a buffer with guanidine thiocyanate and CsCl density gradient centrifugation separated RNA from the rest of the cellular components. Subsequent cholroform/1-butanol extraction and ethanol precipitation were necessary to ensure contaminant-free RNA preparation. Storage of the lysed plant tissue in the buffer with guanidine thiocyanate preserved the sample for two months without noticeable RNA degradation.
홍주봉 (Choo Bong Hong) 한국식물학회 1983 Journal of Plant Biology Vol.26 No.3
Temperature responses of amoebae of thermotactic mutants have been investigated. Amoebae of the mutant strain HO 428 showed positive thermotaxis which is strong at lower temperatures and drops sharply above the growth temperature of amoebae. The temperature response of HO 428 amoebae was not affected by the length of amoebae on the gradients. HO 596 amebae seemed to have both positive and negative thermotactic responses shortly after food depletion. Longer exposure of these amoebae on the thermal gradients induced a stronger negative response at lower temperatures and and apparent positive response at higher temperatures. A similar change could be observed in HO 1445 amoebae. Based on the steady positive thermotactic response by HO 428 amoebae and the mode of change in temperature response at higher temperatures, 24℃ and 26℃, by HO 596 amoebae, a model for the temperature response of vegetative Dictyostelium discoideum amoebae, strain HL 50, has been proposed. The main features of the model are: a positive response at the thermal gradients with midpoint temperatures lower than the growth temperatures of amoebae and a negative response above it.
Hong, Jin,Kim, Bong-Woo,Choo, Hyo-Jung,Park, Jung-Jin,Yi, Jae-Sung,Yu, Dong-Min,Lee, Hyun,Yoon, Gye-Soon,Lee, Jae-Seon,Ko, Young-Gyu American Society for Biochemistry and Molecular Bi 2014 The Journal of biological chemistry Vol.289 No.29
<P>To address whether mitochondrial biogenesis is essential for skeletal myogenesis, C2C12 myogenesis was investigated after knockdown of NADH dehydrogenase (ubiquintone) flavoprotein 1 (NDUFV1), which is an oxidative phosphorylation complex I subunit that is the first subunit to accept electrons from NADH. The NDUFVI knockdown enhanced C2C12 myogenesis by decreasing the NAD<SUP>+</SUP>/NADH ratio and subsequently inactivating SIRT1 and SIRT1 activators (pyruvate, SRT1720, and resveratrol) abolished the NDUFV1 knockdown-induced myogenesis enhancement. However, the insulin-elicited activation of insulin receptor β (IRβ) and insulin receptor substrate-1 (IRS-1) was reduced with elevated levels of protein-tyrosine phosphatase 1B after NDUFV1 knockdown in C2C12 myotubes. The NDUFV1 knockdown-induced blockage of insulin signaling was released by protein-tyrosine phosphatase 1B knockdown in C2C12 myotubes, and we found that NDUFV1 or SIRT1 knockdown did not affect mitochondria biogenesis during C2C12 myogenesis. Based on these data, we can conclude that complex I dysfunction-induced SIRT1 inactivation leads to myogenesis enhancement but blocks insulin signaling without affecting mitochondria biogenesis.</P>