4 results on '"Xiaoyu Wu"'
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2. Low Stability of Nucleocapsid Protein in SARS Virus
- Author
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Yan Fu, Xiaoyu Wu, Yongzhang Luo, Hao Zhou, Yihua Wang, Guiyong Yuan, Bing Li, and Yulong Wang
- Subjects
Protein Denaturation ,Protein Folding ,Circular dichroism ,Hot Temperature ,Acid–base titration ,Sodium Chloride ,Biology ,Severe Acute Respiratory Syndrome ,medicine.disease_cause ,Biochemistry ,chemistry.chemical_compound ,medicine ,Humans ,Urea ,Denaturation (biochemistry) ,Guanidine ,Coronavirus ,RNA ,Cations, Monovalent ,Hydrogen-Ion Concentration ,Nucleocapsid Proteins ,Crystallography ,Severe acute respiratory syndrome-related coronavirus ,chemistry ,Proton NMR ,Thermodynamics ,Virus Inactivation ,Protein folding - Abstract
The nucleocapsid protein (N protein) is one of the major virion structural proteins of a newly identified coronavirus, which has been confirmed as the causative agent of severe acute respiratory syndrome (SARS). The major function of N protein is to assemble the RNA of coronavirus. In the present study, the gene encoding the N protein was cloned and the protein was expressed, purified, and refolded as shown by (1)H NMR measurement. The maximal Trp emission wavelength occurs near 331 nm, suggesting substantial burial of Trp residues. Circular dichroism measurements indicate that N protein contains little alpha-helical structure. Acid titration shows that N protein begins to unfold near pH 5 and is fully denatured near pH 2.7, and the acid unfolding process is reversible. The physical and chemical properties of N protein indicate that its stability is low. N protein is denatured reversibly at pH 7.4 either by urea (with C(m) of 2.77 M and m value of 2.74 kcal mol(-1) M(-1)) or GdmCl (with C(m) of 1.46 M and m value of 4.50 kcal mol(-1) M(-1)). In the heat-induced denaturation in phosphate-buffered saline buffer, N-protein starts to unfold at 35 degrees C and is completely denatured at 55 degrees C, where SARS virus was also reported to be inactivated. We propose that the low stability of N protein may be critical for the stability and function of SARS virus.
- Published
- 2004
3. Acid-induced unfolding mechanism of recombinant human endostatin
- Author
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Qianjie Chen, Bing Li, Xiaoyu Wu, Yongzhang Luo, and Hao Zhou
- Subjects
Circular dichroism ,Protein Denaturation ,Protein Folding ,Time Factors ,Sodium Acetate ,Acid–base titration ,macromolecular substances ,Biochemistry ,Protein Structure, Secondary ,Humans ,Protein secondary structure ,Nuclear Magnetic Resonance, Biomolecular ,Acetic Acid ,Chemistry ,Tryptophan ,Deuterium Exchange Measurement ,Trifluoroethanol ,Hydrogen-Ion Concentration ,Fluorescence ,Recombinant Proteins ,Endostatins ,Protein Structure, Tertiary ,Folding (chemistry) ,Kinetics ,Spectrometry, Fluorescence ,cardiovascular system ,Biophysics ,Proton NMR ,Thermodynamics ,Endostatin - Abstract
Endostatin is a potent angiogenesis inhibitor. The structure of endostatin is unique in that its secondary structure is mainly irregular loops and beta-sheets and contains only a small fraction of alpha-helices with two pairs of disulfide bonds in a nested pattern. We choose human endostatin as a model system to study the folding mechanism of this kind. Nuclear magnetic resonance (NMR), tryptophan emission fluorescence, and circular dichroism (CD) were used to monitor the unfolding process of endostatin upon acid titration. Urea-induced unfolding was used to measure the stability of endostatin under different conditions. Our results show that endostatin is very acid-resistant; some native structure still remains even at pH 2 as evidenced by (1)H NMR. Trifluoroethanol (TFE) destabilizes native endostatin, while it makes endostatin even more acid-resistant in the low pH region. Stability measurement of endostatin suggests that endostatin is still in native structure at pH 3.5 despite the decreased stability. Acid-induced unfolding of endostatin is reversible, although it requires a long time to reach equilibrium below pH 3. Surprisingly, the alpha-helical content of endostatin is increased when it is unfolded at pH 1.6, and the alpha-helical content of the polypeptide chain of unfolded endostatin increases linearly with TFE concentration in the range of 0-30%. This observation indicates that the polypeptide chain of unfolded endostatin has an intrinsic alpha-helical propensity. Our discoveries may provide clues for refolding endostatin more efficiently. The acid-resistance property of endostatin may have biological significance in that it cannot be easily digested by proteases in an acidic environment such as in a lysosome in the cell.
- Published
- 2004
4. Acid-Induced Unfolding Mechanism of Recombinant Human Endostatin.
- Author
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Bing Li, Xiaoyu Wu, Hao Zhou, Qianjie Chen, Bal Ram, and Yongzhang Luo, Bal Ram
- Subjects
- *
NEOVASCULARIZATION , *NUCLEAR magnetic resonance , *FLUORESCENCE , *LYSOSOMES , *PROTEOLYTIC enzymes , *AMINO acids - Abstract
Endostatin is a potent angiogenesis inhibitor. The structure of endostatin is unique in that its secondary structure is mainly irregular loops and β-sheets and contains only a small fraction of α-helices with two pairs of disulfide bonds in a nested pattern. We choose human endostatin as a model system to study the folding mechanism of this kind. Nuclear magnetic resonance (NMR), tryptophan emission fluorescence, and circular dichroism (CD) were used to monitor the unfolding process of endostatin upon acid titration. Urea-induced unfolding was used to measure the stability of endostatin under different conditions. Our results show that endostatin is very acid-resistant; some native structure still remains even at pH 2 as evidenced by ¹H NMR. Trifluoroethanol (TFE) destabilizes native endostatin, while it makes endostatin even more acid-resistant in the low pH region. Stability measurement of endostatin suggests that endostatin is still in native structure at pH 3.5 despite the decreased stability. Acid-induced unfolding of endostatin is reversible, although it requires a long time to reach equilibrium below pH 3. Surprisingly, the α-helical content of endostatin is increased when it is unfolded at pH 1.6, and the α-helical content of the polypeptide chain of unfolded endostatin increases linearly with TFE concentration in the range of 0-30%. This observation indicates that the polypeptide chain of unfolded endostatin has an intrinsic α-helical propensity. Our discoveries may provide clues for refolding endostatin more efficiently. The acid-resistance property of endostatin may have biological significance in that it cannot be easily digested by proteases in an acidic environment such as in a lysosome in the cell. [ABSTRACT FROM AUTHOR]
- Published
- 2004
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