Biomedical subjects

Qingjun Ma

Publications and source records attributed to Qingjun Ma.

At least 19 recordsLinked to original sources

PubMed2006

Application of the use of high-throughput technologies to the determination of protein structures of bacterial and viral pathogens.

The Structural Proteomics In Europe (SPINE) programme is aimed at the development and implementation of high-throughput technologies for the efficient structure determination of proteins of biomedical importance, such as those of bacterial and viral pathogens linked to human health. Despite the challenging nature of some of these targets, 175 novel pathogen protein structures (approximately 220 including complexes) have been determined to date. Here the impact of several technologies on the structural determination of proteins from human pathogens is illustrated with selected examples, including the parallel expression of multiple constructs, the use of standardized refolding protocols and optimized crystallization screens.

Animals↗

PubMed2006

The Mycobacterium tuberculosis LipB enzyme functions as a cysteine/lysine dyad acyltransferase.

Lipoic acid is essential for the activation of a number of protein complexes involved in key metabolic processes. Growth of Mycobacterium tuberculosis relies on a pathway in which the lipoate attachment group is synthesized from an endogenously produced octanoic acid moiety. In patients with multiple-drug-resistant M. tuberculosis, expression of one gene from this pathway, lipB, encoding for octanoyl-[acyl carrier protein]-protein acyltransferase is considerably up-regulated, thus making it a potential target in the search for novel antiinfectives against tuberculosis. Here we present the crystal structure of the M. tuberculosis LipB protein at atomic resolution, showing an unexpected thioether-linked active-site complex with decanoic acid. We provide evidence that the transferase functions as a cysteine/lysine dyad acyltransferase, in which two invariant residues (Lys-142 and Cys-176) are likely to function as acid/base catalysts. Analysis by MS reveals that the LipB catalytic reaction proceeds by means of an internal thioesteracyl intermediate. Structural comparison of LipB with lipoate protein ligase A indicates that, despite conserved structural and sequence active-site features in the two enzymes, 4'-phosphopantetheine-bound octanoic acid recognition is a specific property of LipB.

Acyltransferases↗

PubMed2006

Structural elucidation of the PDI-related chaperone Wind with the help of mutants.

The structures of the PDI-related protein Wind (with a C-terminal His(6) tag) and the mutants Y53S, Y53F and Y55K have been determined and compared with the wild-type structure with the His(6) tag at the N-terminus. All five structures show the same mode of dimerization, showing that this was not an artefact introduced by the nearby N-terminal His(6) tag and suggesting that this dimer may also be the biologically active form. Although the mutants Y53S and Y55K completely abrogate transport of the protein Pipe (which appears to be the primary function of Wind in the cell), only subtle differences can be seen in the putative Pipe-binding region. The Pipe binding in the active forms appears to involve hydrophobic interactions between aromatic systems, whereas the inactive mutants may be able to bind more strongly with the help of hydrogen bonds, which could disturb the delicate equilibrium required for effective Pipe transport.

Amino Acid Substitution↗

PubMed2006

Interaction between c-Abl and Arg tyrosine kinases and proteasome subunit PSMA7 regulates proteasome degradation.

Proteasome-mediated proteolysis is a primary protein degradation pathway in cells. The present study demonstrates that c-Abl and Arg (abl-related gene) tyrosine kinases associate with and phosphorylate the proteasome PSMA7 (alpha4) subunit at Tyr-153. Consequently, proteasome-dependent proteolysis is compromised. Notably, cells expressing a phosphorylation mutant of PSMA7(Y153F) display impaired G1/S transition and S/G2 progression, highlighting the biological significance of tyrosine phosphorylation of a proteasome subunit as an important cellular regulatory control.

Animals↗

PubMed2006

Identification of N-terminal acetylation of recombinant human prothymosin alpha in Escherichia coli.

Functional modification of protein through N-terminal acetylation is common in eukaryotes but rare in prokaryotes. Prothymosin alpha is an essential protein in immune stimulation and apoptosis regulation. The protein is N-terminal acetylated in eukaryotes, but similar modification has never been found in recombinant protein produced in prokaryotes. In this study, two mass components of recombinant human prothymosin alpha expressed in Escherichia coli were identified and separated by RP-HPLC. Mass spectrometry of the two components showed that one of them had a 42 Da mass increment as compared with the theoretical mass of human prothymosin alpha, which suggested a modification of acetylation. The mass of another one was equal to that of the theoretical one. Peptides mass spectrometry of the modified component showed that the 42-Da mass increment occurred in the N-terminal peptide domain, and MS/MS peptide sequencing of the N-terminal peptide found that the acetylated modification occurred at the N-terminal serine residue. So, part of the recombinant human prothymosin alpha produced by E. coli was N-terminal acetylated. This finding adds a new clue for the mechanism of acetylated modification in prokaryotes, and also suggested a new method for production of N-terminal modificated prothymosin alpha and thymosin alpha1.

Acetylation↗

PubMed2006

Aluminacyclopropene: syntheses, characterization, and reactivity toward terminal alkynes.

Reactions of LAl with ethyne, mono- and disubstituted alkynes, and diyne to aluminacyclopropene LAl[eta2-C2(R1)(R2)] ((L = HC[(CMe)(NAr)]2, Ar = 2,6-iPr2C6H3); R1 = R2 = H, (1); R1 = H, R2 = Ph, (2); R1 = R2 = Me, (3); R1 = SiMe3, R2 = C[triple bond]CSiMe3, (4)) are reported. Compounds 1 and 2 were obtained in equimolar quantities of the starting materials at low temperature. The amount of C2H2 was controlled by removing an excess of C2H2 in the range from -78 to -50 degrees C. Compound 4 can be alternatively prepared by the substitution reaction of LAl[eta2-C2(SiMe3)2] with Me3SiC[triple bond]CC[triple bond]CSiMe3 or by the reductive coupling reaction of LAlI2 with potassium in the presence of Me3SiC[triple bond]CC[triple bond]CSiMe3. The reaction of LAl with excess C2H2 and PhC[triple bond]CH (<1:2) afforded the respective alkenylalkynylaluminum compounds LAl(CH=CH2)(C[triple bond]CH) (5) and LAl(CH=CHPh)(C[triple bond]CPh) (6). The reaction of LAl(eta2-C2Ph2) with C2H2 and PhC[triple bond]CH yielded LAl(CPh=CHPh)(C[triple bond]CH) (7) and LAl(CPh=CHPh)(C[triple bond]CPh) (8), respectively. Rationally, the formation of 5 (or 6) may proceed through the corresponding precursor 1 (or 2). The theoretical studies based on DFT calculations show that an interaction between the Al(I) center and the C[triple bond]C unit needs almost no activation energy. Within the AlC2 ring the computational Al-C bond order of ca. 1 suggests an Al-C sigma bond and therefore less pi electron delocalization over the AlC2 ring. The computed Al-eta2-C2 bond dissociation energies (155-82.6 kJ/mol) indicate a remarkable reactivity of aluminacyclopropene species. Finally, the 1H NMR spectroscopy monitored reaction of LAl(eta2-C2Ph2) and PhC[triple bond]CH in toluene-d8 may reveal an acetylenic hydrogen migration process.

Journal Article↗

PubMed2006

Biopharmaceuticals in China.

The biopharmaceutical industry, whose products are produced mainly by recombinant DNA technology, antibody technologies and cytotechnology, is the most important sector in industrial biotechnology, and is one of the most rapidly growing high-tech industries. The global market for biopharmaceuticals had been growing at annual growth rates of 15-33% over the last 8 years, and sales exceeded 55 billion dollars in 2005. This review presents an overview of the Chinese biopharmaceutical industry, listing the global top-selling biopharmaceuticals in 2005, and briefly describes the major biotech drugs approved by the Chinese State Food and Drug Administration, such as recombinant cytokines, therapeutic antibodies, recombinant vaccines, and gene therapy products.

Animals↗

PubMed2005

Ubiquitination and degradation of the Arg tyrosine kinase is regulated by oxidative stress.

The c-Abl and Arg nonreceptor tyrosine kinases are activated in the response of cells to oxidative stress. The present studies demonstrate that treatment of cells with 0.1 mM H2O2 is associated with increased tyrosine phosphorylation of Arg and little effect on Arg levels. By contrast, exposure to 1.0 mM H2O2 decreased Arg phosphorylation. Treatment with 1.0 mM H2O2 was also associated with ubiquitination and degradation of Arg. The results show that Arg is stabilized in response to 0.1 mM H2O2 by autophosphorylation of Y-261, consistent with involvement of the Arg kinase function in regulating Arg levels. The results further demonstrate that c-Abl-mediated phosphorylation of Arg on Y-261 similarly confers Arg stabilization. In concert with these results, phosphorylation of Arg on Y-261 blocked H2O2-induced ubiquitination and thereby Arg degradation and inactivation. These findings demonstrate that Arg phosphorylation and degradation are differentially regulated by the degree of oxidative stress, and that Arg stability is conferred by phosphorylation of Y-261.

Arginine↗

PubMed2005

Characterization of a monoclonal antibody that antagonizes the function of human endostatin.

Endostatin, a 20-kDa proteolytic fragment of collagen XVIII, is a potent inhibitor of angiogenesis and tumor growth. The anti-angiogenic effects of endostatin include inhibition of endothelial cell migration and proliferation, and inhibition of the activity of MMP2. Structure-function analysis of endostatin that implies this contravention function buried in separate fragments of endostatin introduces new issues into the understanding of the structure-function relationship of endostatin. We developed and characterized a novel murine MAb, 4E7, to human endostatin, which antagonizes the function of endostatin. As we show here, MAb 4E7 blocks the anti-migration/adhesion effects of endostatin in vitro and the anti-angiogenesis effect of endostatin in vivo, but the inhibition effect of endostatin on endothelial cell proliferation is not affected by MAb4E7. These results suggest that the anti-migration and anti-proliferation functions of endostatin may have distinct structural foundations.

Animals↗

PubMed2005

Boosting immune response to hepatitis B DNA vaccine by coadministration of Prothymosin alpha-expressing plasmid.

DNA vaccines induce protective humoral and cell-mediated immune responses in several animal models. However, compared to conventional vaccines, DNA vaccines usually induce poor antibody responses. In this study, we report that coadministration of a hepatitis B virus (HBV) DNA vaccine with prothymosin alpha as an adjuvant improves antibody responses to HBV S antigen. We also observed higher seroconversion rates and higher antibody titers. Prothymosin alpha appears to increase the number and affinity of hepatitis B surface antigen-specific, gamma interferon-secreting T cells and to enhance cellular immune response to the PreS2S DNA vaccine. Interestingly, administering the DNA separately from the prothymosin alpha plasmid abrogated the enhancement of DNA vaccine potency. The results suggest that prothymosin alpha may be a promising adjuvant for DNA vaccines.

Adjuvants, Immunologic↗

PubMed2004

Alkali burn causes aldehyde dehydrogenase 3A1 (ALDH3A1) decrease in mouse cornea.

PURPOSE: Aldehyde dehydrogenase 3A1 (ALDH3A1) is the most abundant soluble protein component in the mouse cornea, produced mainly by corneal epithelial cells. High levels of ALDH3A1 in cornea contribute to maintenance of a stable an d transparent corneal structure. Alkali burn is a common damage to the corneal surface, which produces an alkaline hydrolysis of matrix proteins and induces an inflammatory reaction. Our study was intended to detect changes in ALDH3A1 expression after corneal alkaline burn. METHODS: To address this issue we employed RTQ-PCR to monitor the transcriptional change of ALDH3A1 after alkali burn. We used zymography to test enzyme activity changes of ALDH3A1 in the alkali burn cornea; And SDS-PAGE and mass spectrometry technology were used to verify protein content changes and to identify ALDH3A1 protein. RESULTS: Using zymography, ALDH3A1 enzymic activity was observed to decrease immediately after corneal alkali burn and the levels recovered following healing. Proteins extracted from alkali burned corneas, when run on SDS-PAGE, showed the same sized band (about 54 kDa, which is the molecular weight of ALDH3A1) but in much smaller quantity, compared to normal corneas. This result was further verified by mass spectrometry fingerprinting of the in-gel lysis product. An immediate decrease of ALDH3A1 transcription after alkali burning of the cornea was also found using RTQ-PCR. This level of transcription was gradually restored during healing. CONCLUSIONS: Alkali burn of the corneal surface caused a rapid decrease of ALDH3A1 in the corneal at both the RNA and protein levels, which leads to the loses of the protective component of the corneal surface and makes it vulnerable to further damage. The ALDH3A1 level in the cornea gradually recovered during the healing process. Use of an anti-oxidation reagent as a treatment ingredient for alkali burn of the corneal surface could compensate for the decrease of anti-oxidation protection potential caused by ALDH3A1 loss.

Aldehyde Dehydrogenase↗

PubMed2004

A seven-membered aluminum sulfur allenyl heterocycle arising from the conversion of an aluminacyclopropene with CS2.

The reaction of an aluminacyclopropene LAl[eta2-C2(SiMe3)2] (1, L = HC(CMeNAr)2, Ar = 2,6-iPr2C6H3) with CS2 in the temperature range from -78 degrees C to room temperature affords the first seven-membered aluminum sulfur-containing heterocyclic compound [LAl]2(mu-S)[eta2-SC(SiMe3)=C=C(SiMe3)] (2) bearing an allenyl group. The structural characterization of 2 and the analogous compound LAl[OC(O)C2(SiMe3)2] (3) of the proposed intermediate A and the variable-temperature 1H NMR kinetic study of this reaction may give a better understanding on this unusual conversion.

Aluminum↗

PubMed2004

Mapping of a substrate binding site in the protein disulfide isomerase-related chaperone wind based on protein function and crystal structure.

The protein disulfide isomerase (PDI)-related protein Wind is essential in Drosophila melanogaster, and is required for correct targeting of Pipe, an essential Golgi transmembrane 2-O-sulfotransferase. Apart from a thioredoxin fold domain present in all PDI proteins, Wind also has a unique C-terminal D-domain found only in PDI-D proteins. Here, we show that Pipe processing requires dimeric Wind, which interacts directly with the soluble domain of Pipe in vitro, and we map an essential substrate binding site in Wind to the vicinity of an exposed cluster of tyrosines within the thioredoxin fold domain. In vitro, binding occurs to multiple sites within the Pipe polypeptide and shows specificity for two consecutive aromatic residues. A second site in Wind, formed by a cluster of residues within the D-domain, is likewise required for substrate processing. This domain, expressed separately, impairs Pipe processing by the full-length Wind protein, indicating competitive binding to substrate. Our data represent the most accurate map of a peptide binding site in a PDI-related protein available to date and directly show peptide specificity for a naturally occurring substrate.

Amino Acid Sequence↗

PubMed2004

Antibody responses against SARS-coronavirus and its nucleocaspid in SARS patients.

BACKGROUND: SARS-Cov is the etiologic agent of severe acute respiratory syndrome. An understanding of the antibody responses to the viral components is very important for diagnosis and vaccine development. OBJECTIVE: The spectrum of SARS-specific antibody profiles in SARS patients was investigated from 7 to 210 days after the onset of the symptoms. STUDY DESIGN: Serial serum samples from 14 SARS patients were isolated from 7 to 210 days after the onset of the symptoms, and were tested for anti-viral IgG and IgM by indirect immunofluorescence tests (IFA), anti-nucleocaspid antibody by ELISA tests and viral neutralization. RESULTS: Anti-viral (IgG) and anti-nucleocaspid antibodies were observed in 13 of 14 patients at 14 days after the onset of symptoms, and in all 14 patients at 30-210 days thereafter. Anti-viral antibody (IgM) was detected maximally at 30 days, later than that for the IgG class. IgM antibody declined and became undetectable between 60 to 180 days after the onset of the symptoms. Neutralizing viral antibodies were demonstrated in the sera from all of the patients with SARS symptoms. CONCLUSIONS: Anti-viral IgG, IgM, and anti-nucleocaspid antibodies were detected 7-30 days in patients after the onset of SARS symptoms. Anti-viral IgM antibodies disappeared earlier than IgG. Viral neutralization was demonstrated in the sera from the convalescent patients.

Adult↗

PubMed2004

Profile of antibodies to the nucleocapsid protein of the severe acute respiratory syndrome (SARS)-associated coronavirus in probable SARS patients.

Profiles of antibodies to the nucleocapsid protein of the severe acute respiratory syndrome (SARS)-associated coronavirus in 445 probable SARS patients and 3,749 healthy people or non-SARS patients were analyzed by antigen-capturing enzyme-linked immunosorbent assay. Antinucleocapsid antibodies were elucidated in 17.5% of the probable SARS patients 1 to 7 days after the onset of symptoms and in 80% of the patients 8 to 14 days after the onset. About 90% of the probable SARS patients were positive 15 or more days after illness. Antibody titers increased up to 70 days, and high antibody titers were maintained at least for another 3 months. Of the healthy people and non-SARS patients, only seven (0.187%) were weakly positive.

Adult↗

PubMed2003

Simvastatin induces osteoblastic differentiation and inhibits adipocytic differentiation in mouse bone marrow stromal cells.

To clarify the mechanism of the stimulatory effect of statins on bone formation, we investigated the effect of simvastatin, a widely used statin, on osteoblastic and adipocytic differentiation in primary cultured mouse bone marrow stromal cells (BMSCs). Simvastatin treatment enhanced the expression level of mRNA for osteocalcin and protein for osteocalcin and osteopontin, and increased alkaline phosphatase activity significantly (p<0.05). After BMSCs were exposed to an adipocyte differentiation agonist, Oil Red O staining, fluorescence activated cell sorting, and decreased expression level of lipoprotein lipase mRNA showed that treatment with simvastatin significantly inhibits adipocytic differentiation compared to controls that did not receive simvastatin (p<0.05). Lastly, we found that simvastatin induces high expression of BMP(2) in BMSCs. These observations suggested that simvastatin acts on BMSCs to enhance osteoblastic differentiation and inhibits adipocytic differentiation; this effect is at least partially mediated by inducing BMP(2) expression in BMSCs.

Adipocytes↗

PubMed2003

Crystal structure and functional analysis of Drosophila Wind, a protein-disulfide isomerase-related protein.

In the developing Drosophila melanogaster embryo, dorsal-ventral patterning displays an absolute requirement for the product of the essential windbeutel gene, Wind. In homozygous windbeutel mutant flies, dorsal-ventral patterning fails to initiate because of the failure of the Golgi-resident proteoglycan-modifying protein, Pipe, to exit the endoplasmic reticulum, and this leads to the death of the embryo. Here, we describe the three-dimensional structure of Wind at 1.9-A resolution and identify a candidate surface for interaction with Pipe. This represents the first crystal structure of a eukaryotic protein-disulfide isomerase-related protein of the endoplasmic reticulum to be described. The dimeric protein is composed of an N-terminal thioredoxin domain and a C-terminal alpha-helical domain unique to protein-disulfide isomerase D proteins. Although Wind carries a CXXC motif that is partially surface accessible, this motif is redox inactive, and the cysteines are not required for the targeting of Pipe to the Golgi. However, both domains are required for targeting Pipe to the Golgi, and, although the mouse homologue ERp28 cannot replace the function of Wind, exchange of the Wind D-domain with that of ERp28 allows for efficient Golgi transport of Pipe.

Amino Acid Sequence↗

PubMed2003

New synthetic route for organic polyoxometallic clusters: synthetic and structural investigations on the first dumb-bell shaped polyoxozirconium hydroxide with the [Zr9(mu5-O)2(mu3-O)4(mu-O)4(mu-OH)8] core structure.

A new route for organic polyoxometallic clusters describes the first dumb-bell-like organic polyoxozirconium hydroxide [[(Cp*Zr)4(mu5-O)(mu3-O)2(mu-OH)4]2Zr(mu-O)4] x 2C7H8 (2; Cp* = C5Me5) involving the treatment of the Brønsted acidic organozirconium hydroxide [(Cp*Zr)6(mu4-O)(mu-O)4(mu-OH)8] x 2C7H8 (1) with organozirconium compounds.

Journal Article↗