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8. Analysis of the forces which stabilize the active conformation of urokinase-type plasminogen activator

Author

Sun, Ziyong, Liu, Bei-Fang, Chen, Yuhong, Gurewich, Victor, Zhu, Dexu, and Liu, Jian-Ning

Subjects
Plasminogen activators -- Research, Urokinase -- Research, Serine -- Research, Biological sciences, Chemistry
Abstract

It was recently proposed that hydrophobic interactions control the active conformation of serine proteases in the trypsin family (Hedstrom et al. (1996) Biochemistry 35, 4515-23) rather than a charge interaction with Asp next to the active site Ser, as formerly believed. In the present study, certain site-directed mutants of the serine protease zymogen pro-urokinase (pro-UK) and its two-chain enzymatic derivative urokinase (UK) were characterized. The results provide information on the structure-function of the catalytic domain of pro-UK/UK, which is relevant to this controversy. Mutations at [Asp.sup.355(c194)], which eliminated its charge, induced a 6250-fold reduction in the catalytic activity of UK. By contrast, reducing the hydrophobicity at the neoterminal [Ile.sup.159(c16)] of UK had relatively little effect. However, when both the hydrophobicity and the size of the side chain were reduced by a glycine substitution at this position, a major reduction (9090-fold) in the catalytic efficiency of UK occurred. This effect was related to the smaller side chain increasing the cavity and the flexibility of the N-terminus and thereby interfering with its charge interaction with [Asp.sup.355(c194)]. A similar mechanism, rather than a change in hydrophobicity, is believed also to explain the reduction in the stabilization energy of the activation domain observed in a trypsin mutant by Hedstrom et al. (1996). Although hydrophobic interaction facilitated the charge interaction with [Asp.sup.355(c194)], the latter was the primary force which stabilized the active conformation of UK. The charge interaction with [Asp.sup.355(c194)] was also found to be the principal determinant of the intrinsic catalytic activity of single-chain pro-UK. Additionally, the findings confirmed that the [K.sub.M] of pro-UK for its natural substrate was significantly lower than that of UK. Since this same phenomenon was also seen with each of the mutants, the substrate binding pocket of these single-chain zymogens was better formed than that of their two-chain, enzymatic derivatives.

Published
1998

15. Redox reactions of cytochrome c facilitated by silver-imidazole complex

Author

Fan Chun-Hai, Zhu Dexu, Li Gen-Xi, and Zhu Jian-Qin

Subjects
Ethanol, biology, Chemistry, Cytochrome c, Inorganic chemistry, Substrate (chemistry), General Chemistry, Redox, chemistry.chemical_compound, Electrode, Polymer chemistry, biology.protein, Imidazole, Layer (electronics), Chemically modified electrode
Abstract

An imidazole modified silver electrode is prepared by immersing the substrate silver electrode in a 2% imidazole solution of ethanol at 50°C for 10 min. The modified electrode is men swept in a cytochrome c solution and the modified layer takes off because the modified electrode is very unstable. Although the amount of the silver-imidazole complex is very small compared with the amount of cytochrome c in the protein solution, it greatly facilitates redo reactions involving the biomacromolecules.

Published
2010

16. Studies on the interaction between cytochrome c and [Pt-dien]2+

Author

Tang Wenxia, Zhu Dexu, Yao Yiming, and Jiang Lijuan

Subjects
Reaction conditions, biology, Chemistry, Stereochemistry, Cytochrome c, Ferricytochrome c, Biochemistry, Inorganic Chemistry, Metal, Residue (chemistry), Molar ratio, visual_art, visual_art.visual_art_medium, Proton NMR, biology.protein, Binding site
Abstract

The reactions between cytochrome c and [Pt-dien] 2+ under different conditions are reported. It is found that the yield of modified protein derivatives as well as the likely binding sites for platinum complex in cytochrome c are sensitive to the reaction conditions. It is first reported that transition-metal complex [Pt-dien] 2+ can bind to Met 80 residue under mild conditions, which causes the FeS bond of ferricytochrome c to be broken. The binding sites of the platinum complex in the modified protein derivatives were identified by analysis of the molar ratio of the two metal atoms (Pt and Fe), 1 H NMR spectra, and UV-vis spectra.

Published
1995

17. Further studies on the interaction between cytochrome c and K2PtCl4

Author

Sun Ziyong, Tang Wenxia, Zhu Dexu, Xia Zhi-Cheng, and Yang Zhi-Hao

Subjects
biology, Stereochemistry, Cytochrome c, Dimer, chemistry.chemical_element, Ferricytochrome c, Biochemistry, Medicinal chemistry, Inorganic Chemistry, Metal, chemistry.chemical_compound, Monomer, chemistry, Molar ratio, visual_art, biology.protein, visual_art.visual_art_medium, Binding site, Platinum
Abstract

The products of the reaction of ferricytochrome c with K 2 PtCl 4 were separated and purified. Three kinds of cytochrome c derivatives—single-labeled monomer, triple-labeled dimer, and hexa-labeled trimer—were obtained. The binding sites of the platinum complex in these modified protein derivatives were identified by the measurement of the molecular weight, the analysis of the molar ratio of the two metal atoms (Pt and Fe), and the study of the reaction of the His-33 blocked cytochrome c with K 2 PtCl 4 .

Published
1992

19. The regulatory effects of macrophages on colony stimulating factor-1 (CSF-1) production

Author

Zhu Jiang-Qin, Andree Scharfmann, Wu Jiong, Arnold Boersma, Zhu Dexu, Geneviève Lamblin, and Han Kia-Ki

Subjects
Macrophage colony-stimulating factor, Lipopolysaccharides, Oligonucleotides, Bone Marrow Cells, Biology, Biochemistry, Cell Line, Colony-Forming Units Assay, Mice, Colony-Stimulating Factors, Bone Marrow, Sense (molecular biology), medicine, Macrophage, Animals, RNA, Messenger, Fibroblast, Immune Sera, Macrophage Colony-Stimulating Factor, Macrophages, Fibroblasts, Oligonucleotides, Antisense, Molecular biology, In vitro, Culture Media, Mice, Inbred C57BL, Haematopoiesis, medicine.anatomical_structure, Myeloid-derived Suppressor Cell, Bone marrow, Interleukin-1
Abstract

1. 1. By using the anti-sense oligodeoxynucleotide inhibition strategy, we demonstrated that the production of CSF-1 by macrophage was blocked specifically by a CSF-1 anti-sense oligodeoxynucleotide complementary to the 5' end of the coding region of mouse CSF-1 m-RNA transcripts, but not by the CSF-1 mRNA transcripts, but not by the CSF-1 sense oligomer. 2. 2. The LPS-induced condition medium of macrophages treated with CSF-1 anti-sense oligodeoxy-nucleotide retained the capacity of stimulating mouse fibroblast cells and bone marrow cells producing CSF-1 in vitro . 3. 3. In addition to the inhibition of CSF-1 production by macrophages CSF-1 anti-sense oligodeoxy-nucleotide also inhibited the CSF-1 production of fibroblast cells and bone marrow cells stimulated by the macrophages conditioned medium. 4. 4. These results suggest that macrophages stimulate their own development by mediating CSF-1 production at least in three ways: (1) production CSF-1; (2) stimulating fibroblast cells; (3) bone marrow cells to produce CSF-1. There is a positive feedback mechanism for macrophage hematopoiesis and its functional expression.

Published
1990

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