Biomedical subjects

Hong Xue

Publications and source records attributed to Hong Xue.

51 records · Page 3Linked to original sources

PubMed2003

Crystal structure of a DNA binding protein from the hyperthermophilic euryarchaeon Methanococcus jannaschii.

The Sac10b family consists of a group of highly conserved DNA binding proteins from both the euryarchaeotal and the crenarchaeotal branches of Archaea. The proteins have been suggested to play an architectural role in the chromosomal organization in these organisms. Previous studies have mainly focused on the Sac10b proteins from the crenarchaeota. Here, we report the 2.0 A resolution crystal structure of Mja10b from the euryarchaeon Methanococcus jannaschii. The model of Mja10b has been refined to an R-factor of 20.9%. The crystal structure of an Mja10b monomer reveals an alpha/beta structure of four beta-strands and two alpha-helices, and Mja10b assembles into a dimer via an extensive hydrophobic interface. Mja10b has a similar topology to that of its crenarchaeota counterpart Sso10b (also known as Alba). Structural comparison between the two proteins suggests that structural features such as hydrophobic inner core, acetylation sites, dimer interface, and DNA binding surface are conserved among Sac10b proteins. Structural differences between the two proteins were found in the loops. To understand the structural basis for the thermostability of Mja10b, the Mja10b structure was compared to other proteins with similar topology. Our data suggest that extensive ion-pair networks, optimized accessible surface area and the dimerization via hydrophobic interactions may contribute to the enhanced thermostability of Mja10b.

Amino Acid Motifs↗

PubMed2003

GABAergic functions and depression: from classical therapies to herbal medicine.

Classical medications employed to treat depression comprise mostly tricyclic antidepressants (TCAs), specific serotonin reuptake inhibitors (SSRIs) and monoamine oxidase inhibitors (MAOIs), in accord with the recognized involvement of serotonergic and adrenergic systems in depression. Other therapies such as electro-convulsive shock, lithium intake and psychotherapy work via as yet unknown mechanisms. Although GABAergic neurotransmitter systems have not been central to etiological hypotheses for depression, observations are accumulating to suggest that these systems might play an important role in the induction of the disease. Lines of evidence in this regard include interactions between GABAergic and other neurotransmitter systems in depression, GABA levels in patients before and after antidepressant treatments, GABA levels and up/down regulations of GABA receptors in animal models of induced depression, and clinical effects of GABA receptor ligands. Phytomedicines that have a long history of useful applications are drawing increasing attention in pharmaceutical research. Moreover, while drug development is usually focused on single constituent drugs on account of their more accurately predictable physiological responses, complex herbal formulae represent an increasingly important source of drug discovery given the advent of high-throughput screening and specific receptor binding assays. Their active constituents acting on different neurotransmitter systems could be identified, and their therapeutic efficacies tested rigorously. Along with new insights into the underlying mechanisms of depression, the rich abundance of chemical entities from herbs is becoming an inviting resource in the search for effective treatment. This review addresses recent research on the possible role of GABAergic receptors with regard to depression, and potentially antidepressant phytomedicines acting on this class of receptors.

Animals↗

PubMed2003

Cloning and characterization of cholesteryl ester transfer transfer protein isolated from the tree shrew.

OBJECTIVE: To obtain the nucleotide sequence and deduced amino acid sequence of cholesteryl ester transfer protein (CETP) cDNA from the tree shrew (Tupaia glis). METHODS: The cDNA sequence of the tree shrew CETP was obtained by utilizing the technique of switching mechanism at 5' end of RNA transcript (SMART) and rapid amplification of cDNA end (RACE) from the first strand of the cDNA. The amino acid sequence of CETP was deduced from the cDNA sequence and its primary and secondary structures were predicted. RESULTS: The sequence of CETP cDNA from tree shrew (GenBank accession number AF334033) covers 1636 bp, including 178 bp at the 3' end of the untranslated region and a 1458 bp fragment in a coding region, which provides the complete sequence of mature tree shrew CETP, although not the initiator methionine. The first 24 bp encodes a partial signal peptide. The mature protein consists of 477 amino acids and is longer than the human version by one amino acid (Gly318). Comparing this amino acid sequence with those of other animals' CETPs, the identity between tree shrew and human and rabbit CETP is 88% and 82%, respectively. The protein is extremely hydrophobic as it contains many hydrophobic residues, especially at the C-terminal, consistent with its function in the transfer of neutral lipids. The amino acid residues concerning with binding and transferring neutral lipids are highly conserved. There is a deletion of an N-linked glycosylation site at Asn342 in the tree shrew CETP protein that may participate in the removal of peripheral cholesterol and cholesteryl ester by increasing its activity of transferring cholesteryl ester. CONCLUSION: The possible glycosylation in the tree shrew CETP may be involved in the molecular mechanism of its insusceptibility to atherosclerosis.

Amino Acid Sequence↗

PubMed2003

[Study on the relationship between smoking, alcohol intake and hyperlipidemia in fishermen].

OBJECTIVE: To identify the relationship between smoking, alcohol intake and hyperlipidemia in fishermen. METHODS: 115 fishermen were randomly recruited and divided into case and control groups according to the result of blood lipoprotein. A questionnaire was used to record general information and the history of smoking and alcohol intake. Statistics were gathered to compare the difference of lipoprotein and apolipoprotein level between exposure and control groups and to calculate the OR value of smoking and alcohol intake. RESULTS: The OR of smoking was 3.417 (95% CI: 1.132 - 10.308), with significant dosage-effect relationship between smoking index and hyperlipidemia. The serum low density lipoprotein-cholesterol (LDL-C) and apolipoprotein (apo) B levels in smoking group was higher than that of control group. The OR value of alcohol intake at early age (early than 20) were 3.275 (95% CI: 1.249 - 8.580) and 4.016 (95% CI: 1.475 - 10.952) respectively. The LDL-C, apoB, the serum total cholesterol (TC)/high density lipoprotein-cholesterol (HDL-C) levels in alcohol abuse group were higher than that of control group. CONCLUSION: Smoking and alcohol abuse were important risk factors of hyperlipidemia, through changing the level of LDL-C and apoB. There was synergistic action between smoking and alcohol abuse in the development of hyperlipidemia.

Adolescent↗

PubMed2002

Anxiolytic effect of wogonin, a benzodiazepine receptor ligand isolated from Scutellaria baicalensis Georgi.

The search for novel anxiolytics devoid of undesirable side-effects typical of classical benzodiazepines (BDZs) has been intense, and flavonoids, as a relative new class of ligands, have been shown to possess anxiolytic effects in vivo. The present study evaluated the pharmacological properties of a naturally occurring monoflavonoid, 5,7-dihydroxy-8-methoxyflavone or wogonin. The affinity (K(i)) of wogonin for the benzodiazepine site (BZD-S) on the gamma-aminobutyric acid(A) (GABA(A)) receptor complex was 0.92 microM. Using electrophysiological techniques, we showed that wogonin enhanced the GABA-activated current in rat dorsal root ganglion neurons, and in Xenopus laevis oocytes expressing recombinant rat GABA(A) receptors, the enhancement was partially reversed by the co-application of a 1 microM concentration of the BZD-S antagonist anexate (Ro15-1788). Acute toxicity and behavioral effects were examined in mice. Acute lethal activity was low, with an LD(50) of 3.9 g/kg. Oral administration of wogonin (7.5 to 30 mg/kg) elicited an anxiolytic response that was similar to that elicited by diazepam in the elevated plus-maze; a dose-dependent increase in open arm entries and time spent in open arms was observed. More importantly, its anxiolytic effect was blocked by the co-administration of Ro15-1788. In the holeboard test, not only did wogonin-treated mice experience an increased number of head-dips but they also spent more time at it, showing no signs of sedation. Furthermore, wogonin did not cause myorelaxant effects in the horizontal wire test. Taken together, these data suggest that wogonin exerts its anxiolytic effect through positive allosteric modulation of the GABA(A) receptor complex via interaction at the BZD-S. Its anxiolytic effect was not accompanied by sedative and myorelaxant side-effects typical of BDZs.

Animals↗

PubMed2002

Expression, purification, crystallization and preliminary X-ray analysis of a DNA-binding protein from Methanococcus jannaschii.

A small DNA-binding protein of 87 amino-acid residues from the hyperthermophilic archaeon Methanococcus jannaschii (Mja10b) was cloned and overexpressed in Escherichia coli. The protein was crystallized and the crystals belong to the space group P6(1)22/P6(5)22, with unit-cell parameters a = b = 50.85, c = 124.02 A, alpha = beta = 90, gamma = 120 degrees. The crystals diffracted to a maximum resolution of 2.2 A at 100 K using Cu Kalpha radiation. The presence of one molecule per asymmetric unit gives a crystal volume per protein mass (V(M)) of 2.4 A(3) Da(-1) and a solvent content of 49% by volume. A full set of X-ray diffraction data was collected to 2.2 A from the native crystal.

Crystallography, X-Ray↗

PubMed2002

NMR analysis of bovine tRNATrp: conformation dependence of Mg2+ binding.

NMR was used to study the solution structure of bovine tRNA(Trp) hyperexpressed in Escherichia coli. With the use of (15)N labeling and site-directed mutagenesis to assign overlapping resonances through the base pair replacement of U(71)A(2) by G(2)C(71), U(27)A(43) by G(27)C(43), and G(12)C(23) by U(12)A(23), the resonances of all 26 observable imino protons in the helical regions and in the tertiary interactions were assigned unambiguously by means of two-dimensional nuclear Overhauser effect spectroscopy and heteronuclear single quantum coherence methods. When the discriminator base A(73) and the G(12)C(23) base pair on the D stem, two identity elements on bovine tRNA(Trp) that are important for effective recognition by tryptophanyl-tRNA synthetase, were mutated to the ineffective forms of G(73) and U(12)A(23), respectively, NMR analysis revealed an important conformational change in the U(12)A(23) mutant but not in the G(73) mutant molecule. Thus A(73) appears to be directly recognized by tryptophanyl-tRNA synthetase, and G(12)C(23) represents an important structural determinant. Mg(2+) effects on the assigned resonances of imino protons allowed the identification of strong, medium, and weak Mg(2+) binding sites in tRNA(Trp). Strong Mg(2+) binding modes were associated with the residues G(7), s(4)U(8) (where s(4)U is 4-thiouridine), G(12), and U(52). The observations that G(42) was associated with strong Mg(2+) binding in only the U(12)A(23) mutant tRNA(Trp) but not the wild type or G(73) mutant tRNA(Trp) and that the G(7), s(4)U(8), G(24), and G(22) imino protons are associated with a two-site Mg(2+) binding mode in wild type and G(73) mutant but only a one-site mode in the U(12)A(23) mutant established the occurrence of conformational change in the U(12)A(23) mutant tRNA(Trp). These observations also established the dependence of Mg(2+) binding on tRNA conformation and the usefulness of Mg(2+) binding sites as conformational probes. The thermal titration of tRNA(Trp) in the presence and absence of 10 mm Mg(2+) indicated that overall tRNA(Trp) structure stability was increased by more than 15 degrees C by the presence of Mg(2+).

Animals↗

PubMed2002

Recognition by tryptophanyl-tRNA synthetases of discriminator base on tRNATrp from three biological domains.

To study the recognition by tryptophanyl-tRNA synthetase (TrpRS) of tRNA(Trp) discriminator base, mutations were introduced into the discriminator base of Bacillus subtilis, Archeoglobus fulgidus, and bovine tRNA(Trp), representing the three biological domains. When B. subtilis, A. fulgidus, and human TrpRS were used to acylate these tRNA(Trp), two distinct preference profiles regarding the discriminator base of different tRNA(Trp) substrates were found: G>A>U>C for B. subtilis TrpRS, and A>C>U>G for A. fulgidus and human TrpRS. The preference for G73 in tRNA(Trp) by bacterial TrpRS is much stronger than the modest preferences for A73 by the archaeal and eukaryotic TrpRS. Cross-species reactivities between TrpRS and tRNA(Trp) from the three domains were in accordance with the view that the evolutionary position of archaea is intermediate between those of eukarya and bacteria. NMR spectroscopy revealed that mutation of A73 to G73 in bovine tRNA(Trp) elicited a conformational alteration in the G1-C72 base pair. Mutation of G1-C72 to A1-U72 or disruption of the G1-C72 base pair also caused reduction of Trp-tRNA(Trp) formation. These observations identify a tRNA(Trp) structural region near the end of acceptor stem comprising A73 and G1-C72 as a crucial domain required for effective recognition by human TrpRS.

Animals↗

PubMed2002

Structure-activity relationships of flavonoids, isolated from Scutellaria baicalensis, binding to benzodiazepine site of GABA(A) receptor complex.

Twenty-six flavonoids were isolated from Scutellaria baicalensis. Their affinities for the benzodiazepine (BDZ) binding site of GABA A receptor have been studied using [ 3H]flunitrazepam binding to rat cortical membranes in vitro. The structure-activity relationships suggested that 2'-OH flavones exhibited the most potent binding affinity, which could lead to the design and discovery of new BDZ receptor ligands.

Animals↗

PubMed2002

Two beta-rich structural domains in GABA(A) receptor alpha(1) subunit with different physical properties: Evidence for multidomain nature of the receptor.

The type A gamma-aminobutyric acid (GABA(A)) receptor is a major inhibitory neurotransmitter-gated ion channel. Previously, we identified a membrane-proximal beta-rich (MPBR) domain in fragment C166-L296 of GABA(A) receptor alpha(1) subunit, forming nativelike pentamers. In the present study, another structural domain, the amino-terminal domain, was shown to exist in the fragment Q28-E165. The secondary structures of both fragments were beta-rich as measured using FTIR spectroscopy and estimated from the CD spectra to be 42% and 51% beta-strand for Q28-E165 and C166-L296, respectively. The CD spectrum of the combined fragment Q28-L296 was additive of the spectra of the two fragments. In addition, denaturation curves of both fragments were characteristic of cooperative transitions, supporting their domainlike nature. C166-L296 required 6.5 M of guanidine chloride for total denaturation, therefore it is extraordinarily stable, more so than Q28-E165. Moreover, effects of detergent on the molecular masses of Q28-E165 and C166-L296, as monitored using laser-scattering spectroscopy, indicated that intermolecular interactions were much more significant in C166-L296 than in Q28-E165. Effects of pH on their molecular masses suggested that ionic forces were involved in these interactions. Together the results show that the two adjacent fragments form independent folding units, MPBR and amino-terminal domains, different in secondary structure content, denaturation profile, and polymerization status, and suggest that the former may play a more important role in receptor assembly and that the extraordinary stability may underlie its intrinsic tendency to form oligomers. More significantly, the present study has provided direct evidence for the long-postulated multidomain nature of this family of receptors.

Animals↗

PubMed2002

Blood pressure and mesenteric resistance arterial function after spaceflight.

Ground studies indicate that spaceflight may diminish vascular contraction. To examine that possibility, vascular function was measured in spontaneously hypertensive rats immediately after an 18-day shuttle flight. Isolated mesenteric resistance arterial responses to cumulative additions of norepinephrine, acetylcholine, and sodium nitroprusside were measured using wire myography within 17 h of landing. After flight, maximal contraction to norepinephrine was attenuated (P < 0.001) as was relaxation to acetylcholine (P < 0.001) and sodium nitroprusside (P < 0.05). At high concentrations, acetylcholine caused vascular contraction in vessels from flight animals but not in vessels from vivarium control animals (P < 0.05). The results are consistent with data from ground studies and indicate that spaceflight causes both endothelial-dependent and endothelial-independent alterations in vascular function. The resulting decrement in vascular function may contribute to orthostatic intolerance after spaceflight.

Acetylcholine↗

PubMed2002

[Differentially expressed genes in vascular endothelial cell line ECV 304 induced by high density lipoprotein].

OBJECTIVE: To isolate and clone the differentially expressed genes in vascular endothelial cell induced by high density lipoprotein (HDL) so as to study the anti- atherogenesis molecular mechanism of HDL. METHODS: Differential display reverse transcription PCR method was used to analyze the differentially expressed cDNA in vascular endothelial cell line ECV 304 induced by HDL. After sequencing and homology research, several differentially expressed cDNA fragments were confirmed by Northern blot analysis. RESULTS: Up-regulated and down-regulated cDNA fragments in ECV 304 induced by HDL were isolated. Nine cDNA fragments were highly homologous to the known human genes and four were fragments of novel genes. The known up-regulated genes included genes of human STE20-like kinase, PBK1 protein, transglutaminase, myosin alkali light chain, apobec-1 binding protein 1, and death- associated protein (DAP). The known down-regulated genes included genes of ribosomal protein L7a (RPL7A), voltage-dependent anion channel isoform 2, and glycinamide ribonucleotide transformylase. Northern blot analysis revealed that the expression levels of transglutaminase and apobec-1 binding protein 1 were upregulated by 50% and 70% respectively. CONCLUSION: HDL upregulates the expression of apobec-1 binding protein 1 and transglutaminase in endothelial cells. The high level expression of transglutaminase and apobec-1 binding protein 1 in endothelial cells induced by HDL may be related to anti-atherogenesis function of HDL.

Blotting, Northern↗

PubMed2002

Two flavones from Scutellaria baicalensis Georgi and their binding affinities to the benzodiazepine site of the GABAA receptor complex.

A new flavone 6,2'-dihydroxy-5,7,8,6'-tetramethoxyflavone (1) together with one known flavone 5,7,2'-trihydroxy-6,8-dimethoxyflavone (2) were isolated from the roots of Scutellaria baicalensis Georgi. Their structures were elucidated on the basis of spectral evidence and their affinities for the benzodiazepine (BDZ) site of the GABAA receptor complex were evaluated with a radioligand receptor binding assay.

Animals↗

PubMed2002

[Clinical research of genetic counseling].

To supply reliable materials for the assessment of recurrence risk,prenatal diagnosis and the supervision of high risk persons,we analyzed 10811 patients with the methods of cytogenetics,fluorescent in situ hybridization and molecular genetic PCR methods. The result of cytogenetics:there were 555 abnormal karyotypes of peripheral blood on 5390 cases (10.30%);In 2171 patients who asked for prenatal diagnosis,145 abnormal karyotypes were found (6.68%);We also karyotyped chorionic villous cells of 62 patients with spontaneous abortion and found 28 abnormal karyotypes (45.16%). The PCR results of 23 patients with Down's syndrome were all positive while the results of 155 normal persons were all negative. The method of cytogenetics is very important for diagnosis of abnormal karyotypes;Molecular genetic methods by PCR and FISH are quick,convenient and applicable way.

English Abstract↗

PubMed1998

The cDNA Sequence and Its Tissue Expression of Tree Shrew Apolipoprotein CI.

The mRNA was isolated and purified from tree shrew (TS) liver tissue. A cDNA library of the liver tissue was then constructed by using the mRNA as the template by reverse transcription. Two apolipoprotein CI (apoCI) cDNA clones were identified in the library with an anti-serum to TS apoCI. Sequencing and analysizing of the clones showed that both were the apoCI cDNA sequences in which the larger one was determined as 380 nucleotides. It contains 21 bp and 95 bp in 5' and 3' untranslated regions respectively, and 264 bp in an open reading frame, encoding an 88 aa apoCI precursor (a 26 aa signal peptide, and a 62 aa mature protein whose length is the same as those of rat, mouse and dog, but longer than those of human and baboon by 5 aa residues). The function domains in the protein sequence deduced from the cDNA were predicted by comparison of conservative regions in apoCIs from different species. The results of Northern blot indicated in TS the presence of apoCI mRNA not just mainly in the liver but also found in the intestine, suggesting the mRNA distribution different from those in other mammals and primates.

Journal Article↗