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ABSTRACT: AhV_aPA, the acidic PLA2 purified from Agkistrodon halys pallas venom, was previously reported to possess a strong enzymatic activity and can remarkably induce a further contractile response on the 60 mM K(+)-induced contraction with an EC50 in 369 nM on mouse thoracic aorta rings. In the present study, we found that the p-bromo-phenacyl-bromide (pBPB), which can completely inhibit the enzymatic activity of AhV_aPA, did not significantly reduce the contractile response on vessel rings induced by AhV_aPA, indicating that the vasoconstrictor effects of AhV_aPA are independent of the enzymatic activity. The inhibitor experiments showed that the contractile response induced by AhV_aPA is mainly attributed to the Ca(2+) releasing from Ca(2+) store, especially sarcoplasmic reticulum (SR). Detailed studies showed that the Ca(2+) release from SR is related to the activation of inositol trisphosphate receptors (IP3Rs) rather than ryanodine receptors (RyRs). Furthermore, the vasoconstrictor effect could be strongly reduced by pre-incubation with hepain, indicating that the basic amino acid residues on the surface of AhV_aPA may be involved in the interaction between AhV_aPA and the molecular receptors. These findings offer new insights into the functions of snake PLA2 and provide a novel pathogenesis of A. halys pallas venom.
Toxicon 05/2013; · 2.51 Impact Factor
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ABSTRACT: Human RNA-binding protein (HuR), a ubiquitously expressed member of the Hu protein family, plays an important role in mRNA degradation and has been implicated as a key post-transcriptional regulator. HuR contains three RNA-recognition motif (RRM) domains. The two N-terminal tandem RRM domains can selectively bind AU-rich elements (AREs), while the third RRM domain (RRM3) contributes to interactions with the poly-A tail of target mRNA and other ligands. Here, the X-ray structure of two methylated tandem RRM domains (RRM1/2) of HuR in their RNA-free form was solved at 2.9 Å resolution. The crystal structure of RRM1/2 complexed with target mRNA was also solved at 2.0 Å resolution; comparisons of the two structures show that HuR RRM1/2 undergoes conformational changes upon RNA binding. Fluorescence polarization assays (FPA) were used to study the protein-RNA interactions. Both the structure and the FPA analysis indicated that RRM1 is the primary ARE-binding domain in HuR and that the conformational changes induce subsequent contacts of the RNA substrate with the inter-domain linker and RRM2 which greatly improve the RNA-binding affinity of HuR.
Acta crystallographica. Section D, Biological crystallography 03/2013; 69(Pt 3):373-80. · 12.67 Impact Factor
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ABSTRACT: Phospholipases A(2) (PLA(2)s) are the major component of snake venoms and exert a variety of relevant toxic actions such as neurotoxicity and myotoxicity, amongst others. An acidic PLA(2), here named AhV_aPA, was purified from Agkistrodon halys pallas venom by means of a three-step chromatographic procedure. AhV_aPA migrated as a single band on SDS-PAGE gels, with a molecular weight of about 14 kDa. Like other acidic aPLA(2)s, AhV_aPA has high enzymatic activity. Tension measurements of mouse thoracic aortic rings remarkably indicated that AhV_aPA could induce a further contractile response on the 60 mM K(+)-induced contraction, with an EC(50) of 369 nmol l(-1). Rod-shaped crystals were obtained by the hanging-drop vapour-diffusion method and diffracted to a resolution limit of 2.30 Å. The crystals belonged to space group P222, with unit-cell parameters a = 44.27, b = 68.39, c = 81.54 Å.
Acta Crystallographica Section F Structural Biology and Crystallization Communications 11/2012; 68(Pt 11):1329-1332. · 0.51 Impact Factor
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ABSTRACT: The Drosophila melanogaster eukaryotic translation initiation factor 5C domain-containing protein (ECP) is composed of two independently folded domains which belong to the basic leucine-zipper and W2 domain-containing protein (BZW) family. Based on the sequence similarity between the C-terminal W2 domain of ECP and some eukaryotic translation initiation factors (such as eIF2Bℇ, eIF4γ, eIF5 etc.), ECP has been speculated to participate in the translation initiation process. Structural information on the C-terminal W2 domain of ECP would be helpful in understanding the specific cellular function of this protein. Here, the W2 domain of ECP was expressed and crystallized. Crystals grown by the hanging-drop vapour-diffusion method diffracted to 2.70 Å resolution and belonged to space group I4, with unit-cell parameters a = b = 81.05, c = 57.44 Å. The Matthews coefficient suggested that there was one molecule per asymmetric unit in the crystal.
Acta Crystallographica Section F Structural Biology and Crystallization Communications 11/2012; 68(Pt 11):1315-1317. · 0.51 Impact Factor
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ABSTRACT: A snake venom thrombin-like enzyme (SVTLE) from Agkistrodon halys pallas venom was isolated by means of a two-step chromatographic procedure. The purified enzyme, named AhV_TL-I, showed fibrinogenolytic activity against both the Aα and Bβ chains of bovine fibrinogen. Unlike the other SVTLEs, AhV_TL-I has poor esterolytic activity upon BAEE substrate. The N-terminal sequence of AhV_TL-I was determined to be IIGGDEXNINEHRFLVALYT, and the molecular mass was confirmed to 29389.533 Da by MALDI-TOF mass spectrometry. Its complete cDNA and derived amino acid sequence were obtained by RT-PCR. The crystal structure of AhV_TL-I was determined at a resolution of 1.75 Å. A disaccharide was clearly mapped in the structure, which involved in regulating the esterolytic activity of AhV_TL-I. The presence of the N-glycan deformed the 99-loop, and the resulting steric hindrances hindered the substrates to access the active site. Furthermore, with the carbohydrate moiety, AhV_TL-I could induce mouse thoracic aortic ring contraction with the EC(50) of 147 nmol/L. Besides, the vasoconstrictor effects of AhV_TL-I were also independent of the enzymatic activity. The results of [Ca(2+)](i) measurement showed that the vasoconstrictor effects of AhV_TL-I were attributed to Ca(2+) releasing from Ca(2+) store. Further studies showed that it was related to the activation of ryanodine receptors (RyRs). These offer new insights into the snake SVTLEs functions and provide a novel pathogenesis of A. halys pallas venom.
Archive für Toxikologie 10/2012; · 4.67 Impact Factor
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ABSTRACT: Palmitoylation/depalmitoylation plays an important role in protein modification. yApt1 is the only enzyme in Saccharomyces cerevisiae that catalyses depalmitoylation. In the present study, recombinant full-length yApt1 was cloned, expressed, purified and crystallized. The crystals diffracted to 2.40 Å resolution and belonged to space group P4(2)2(1)2, with unit-cell parameters a = b = 146.43, c = 93.29 Å. A preliminary model of the three-dimensional structure has been built and further refinement is ongoing.
Acta Crystallographica Section F Structural Biology and Crystallization Communications 07/2012; 68(Pt 7):775-7. · 0.51 Impact Factor
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ABSTRACT: The yeast Shu complex, consisting of the proteins Shu1, Shu2, Psy3, and Csm2, maintains genomic stability by coupling post-replication repair to homologous recombination. However, a lack of biochemical and structural information on the Shu proteins precludes revealing their precise roles within the pathway. Here, we report on the 1.9-Å crystal structure of the Psy3-Csm2 complex. The crystal structure shows that Psy3 forms a heterodimer with Csm2 mainly through a hydrophobic core. Unexpectedly, Psy3 and Csm2 share a similar architecture that closely resembles the ATPase core domain of Rad51. The L2 loop present in Psy3 and Csm2 is similar to that of Rad51 and confers the DNA binding activity of the Shu complex. As with Rad51, the Shu complex appears to form a nucleoprotein filament by binding nonspecifically to DNA. Structure-based mutagenesis studies have demonstrated that the DNA binding activity of the Shu complex is essential for repair of the methyl methanesulfonate-induced DNA damage. Our findings provide good foundations for the understanding of the Srs2 regulation by the Shu complex.
Journal of Biological Chemistry 03/2012; 287(24):20231-9. · 4.77 Impact Factor
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ABSTRACT: The Saccharomyces cerevisiae NAD(+)-dependent deacetylase HST1 belongs to the class III HDAC family; it acts as a transcriptional corepressor for the specific middle sporulation and de novo NAD(+)-biosynthesis genes and also takes part in the SET3C and SUM1-RFM1-HST1 complexes. Structural information on HST1 and its related complexes would be helpful in order to understand the structural basis of its deacetylation mechanism and the assembly of these complexes. Here, HST1(156-503) was expressed and crystallized. Crystals grown by the hanging-drop vapour-diffusion method diffracted to 2.90 Å resolution and belonged to space group P2(1), with unit-cell parameters a = 40.2, b = 101.7, c = 43.9 Å, β = 103.9°. Both Matthews coefficient analysis and the self-rotation function suggested the presence of four molecules per asymmetric unit in the crystal, with a solvent content of 49.76% (V(M) = 2.45 Å(3) Da(-1)).
Acta Crystallographica Section F Structural Biology and Crystallization Communications 12/2011; 67(Pt 12):1579-81. · 0.51 Impact Factor
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ABSTRACT: Human Pax2 transactivation domain-interacting protein (hPTIP), containing six BRCT domains, is an essential protein required for the IR induced DDR process with an unclear role. Here we report that the tandem BRCT5-BRCT6 domain of hPTIP recognizes the γH2AX tail, and this interaction depends on the phosphorylation of H2AX Ser139 and binding with the carboxyl ending peptide to the aminoacyl ending peptide. The 2.15 Å crystal structure of hPTIP BRCT5/6-γH2AX complex and mutation analysis provide molecular evidence for direct interactions between PTIP and γH2AX. This interaction proffers a new clue to identify the role of PTIP in DDR pathways.
FEBS letters 11/2011; 585(24):3874-9. · 3.54 Impact Factor
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ABSTRACT: SNARE proteins are crucial for membrane fusion in vesicular transport. To ensure efficient and accurate fusion, SNAREs need to be sorted into different budding vesicles. This process is usually regulated by specific recognition between SNAREs and their adaptor proteins. How different pairs of SNAREs and adaptors achieve their recognition is unclear. Here, we report the recognition between yeast SNARE Vti1p and its adaptor Ent3p derived from three crystal structures. Surprisingly, this yeast pair Vti1p/Ent3p interacts through a distinct binding site compared to their homologues vti1b/epsinR in mammals. An opposite surface on Vti1p_Habc domain binds to a conserved area on the epsin N-terminal homology (ENTH) domain of Ent3p. Two-hybrid, in vitro pull-down and in vivo experiments indicate this binding interface is important for correct localization of Vti1p in the cell. This previously undescribed discovery that a cargo and adaptor pair uses different binding sites across species suggests the diversity of SNARE-adaptor recognition in vesicular transport.
Proceedings of the National Academy of Sciences 07/2011; 108(30):12277-82. · 9.68 Impact Factor
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ABSTRACT: UbiG, an O-methyltransferase from the ubiquinone-biosynthesis pathway in Escherichia coli, catalyzes two O-methyl transfer steps. The primary structures of the O-methyltransferase enzyme family used in ubiquinone synthesis are conserved in both prokaryotes and eukaryotes, but their tertiary structures and catalytic mechanisms are not yet known. Here, UbiG with an N-terminal hexahistidine tag was expressed and crystallized. Crystals grown by the hanging-drop vapour-diffusion method diffracted to 2.00 Å resolution and belonged to space group C121, with unit-cell parameters a = 119.8, b = 58.6, c = 40.2 Å, β = 105.3°. Both Matthews coefficient analysis and the self-rotation function suggested the presence of one molecule per asymmetric unit in the crystal, with a solvent content of 50.52% (V(M) = 2.48 Å(3) Da(-1)).
Acta Crystallographica Section F Structural Biology and Crystallization Communications 06/2011; 67(Pt 6):727-9. · 0.51 Impact Factor
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ABSTRACT: Human antigen R (HuR), a ubiquitously expressed member of the Hu protein family, is an important post-transcriptional regulator which has three RNA-recognition motif (RRM) domains. The two tandem N-terminal RRM domains can selectively bind to the AU-rich element (ARE), while the third one interacts with the poly(A) tail and other proteins. Here, the recombinant ARE-binding region of HuR (residues 18-186) was crystallized in space group P2(1)2(1)2, with unit-cell parameters a = 41.2, b = 133.1, c = 31.4 Å. X-ray diffraction data were collected to a resolution of 2.8 Å. Mutagenesis analysis and SPR assays revealed its poly(U)-binding properties.
Acta Crystallographica Section F Structural Biology and Crystallization Communications 05/2011; 67(Pt 5):546-50. · 0.51 Impact Factor
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ABSTRACT: The cleavage factor I(m) (CF I(m)), consists of a 25 kDa subunit (CF I(m)25) and one of three larger subunits (CF I(m)59, CF I(m)68, CF I(m)72), and is an essential protein complex for pre-mRNA 3'-end cleavage and polyadenylation. It recognizes the upstream sequence of the poly(A) site in a sequence-dependent manner. Here we report the crystal structure of human CF I(m), comprising CF I(m)25 and the RNA recognition motif domain of CF I(m)68 (CF I(m)68RRM), and the crystal structure of the CF I(m)-RNA complex. These structures show that two CF I(m)68RRM molecules bind to the CF I(m)25 dimer via a novel RRM-protein interaction mode forming a heterotetramer. The RNA-bound structure shows that two UGUAA RNA sequences, with anti-parallel orientation, bind to one CF I(m)25-CF I(m)68RRM heterotetramer, providing structural basis for the mechanism by which CF I(m) binds two UGUAA elements within one molecule of pre-mRNA simultaneously. Point mutation and kinetic analyses demonstrate that CF I(m)68RRM can bind the immediately flanking upstream region of the UGUAA element, and CF I(m)68RRM binding significantly increases the RNA-binding affinity of the complex, suggesting that CF I(m)68 makes an essential contribution to pre-mRNA binding.
Cell Research 04/2011; 21(7):1039-51. · 8.19 Impact Factor
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ABSTRACT: Among the known covalent damages that can occur spontaneously to proteins, the formation of isoaspartyl linkages through deamidation of asparagines and isomerization of aspartates may be one of the most rapid forms under conditions of physiological pH and temperature. The protein L-isoaspartyl methyltransferase (PIMT) is thought to recognize L-isoaspartyl residues and repair this kind of damaged proteins. Curiously, there is a potential functional difference between bacterial and mammalian PIMTs. Herein, we present the crystal structure of Escherichia coli PIMT (EcPIMT) at a resolution of 1.8 Å. The enzyme we investigated was able to remain bound to its product S-adenosylhomocysteine (SAH) during crystallization. Analysis indicates that the high affinity of EcPIMT for SAH might lead to the lower activity of the enzyme.
Cell biochemistry and biophysics 12/2010; 58(3):163-7. · 3.34 Impact Factor
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ABSTRACT: Different assemblies of accessory proteins with clathrin are critical for transporting precisely various cargos between intracellular compartments. GGA proteins are adaptors for clathrin-mediated intracellular trafficking, connecting other accessory and cargo proteins to clathrin-coated vesicles. Both binding to the GAE domain of GGA protein yGGA2 in Saccharomyces cerevisia, Ent3 and Ent5 are involved in different trafficking pathways. Ent5 is ubiquitous and localized in a manner independent of yGGA2, and Ent3 functions preferentially through yGGA2. Not known are the sources of these differences. Here we show not all acidic-phenylalanine motifs in Ent3/5 are active for yGGA2_GAE domain binding. Two of the three acidic-phenylalanine motifs from Ent3 can bind to the yGGA2_GAE domain, while only one of the two motifs from Ent5 can bind. We also determined the crystal structure of the yGGA2_GAE domain at 1.8 A resolution. Structural docking and mutagenesis analysis shows inactive motifs in Ent3 and Ent5 repel yGGA2_GAE binding through disfavored residues at positions 1 and 3. These results suggest accessory proteins may fine-tune the GGA adaptor dependence by adjusting their non-acidic-phenylalanine residues, thus contributing to the distinct role of Ent3 and Ent5 in trafficking.
Biochemistry 09/2010; 49(36):7949-55. · 3.42 Impact Factor
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ABSTRACT: Yeast poly(U)-binding protein (Pub1) is a major nuclear and cytoplasmic protein that contains three RNA recognition motif (RRM) domains (termed Pub1RRM1, Pub1RRM2 and Pub1RRM3). Pub1 has been implicated as a regulator of cellular mRNA decay. Nearly 10% of all yeast mRNA decay occurs in a Pub1-dependent manner. Pub1 binds to and stabilizes AU-rich element (ARE) and ARE-like sequence-containing transcripts by protecting them from degradation through the deadenylation-dependent pathway, and also binds to and stabilizes stabilizer element (STE)-containing transcripts by preventing their degradation via the nonsense-mediated decay (NMD) pathway. RNA-binding analyses showed that Pub1 binds to poly(U) in vitro. Here we show the crystal structures of Pub1RRM2 and the first two tandem RRM domains (Pub1RRM12). Crystallography showed that the structure of Pub1RRM12 is a domain-swapped dimer. Size exclusion chromatography assay and analytical ultracentrifugation (AUC) showed that Pub1RRM12 is a monomer in solution. Kinetic analysis showed that all three individual RRM domains can bind to poly(U) with similar affinities and Pub1RRM12 binds to a long poly(U) segment with higher affinity. Mutagenesis analysis revealed that residues on the beta-sheets of Pub1RRM1 and Pub1RRM2 are critical for poly(U) binding.
Journal of Structural Biology 05/2010; 171(3):291-7. · 3.41 Impact Factor
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ABSTRACT: In archaea and eukaryotes, the nascent polypeptide-associated complex (NAC) is one of the cytosolic chaperones that contact the nascent polypeptide chains as they emerge from the ribosome and assist in post-translational processes. The eukaryotic NAC is a heterodimer, and its two subunits form a stable complex through a dimerizing domain called the NAC domain. In addition to acting as a protein translation chaperone, the NAC subunits also function individually in transcriptional regulation. Here we report the crystal structure of the human NAC domain, which reveals the manner of human NAC dimerization. On the basis of the structure, we identified a region in the NAC domain of the human NAC alpha-subunit as a new nucleic acid-binding region, which is blocked from binding nucleic acids in the heterodimeric complex by a helix region in the beta-subunit.
Biochemistry 03/2010; 49(13):2890-6. · 3.42 Impact Factor
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Yiwei Liu,
Hongda Huang,
Bo O Zhou,
Shan-Shan Wang,
Yingxia Hu, Xu Li,
Jianping Liu,
Jianye Zang,
Liwen Niu,
Jihui Wu,
Jin-Qiu Zhou,
Maikun Teng,
Yunyu Shi
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ABSTRACT: Rtt106p is a Saccharomyces cerevisiae histone chaperone with roles in heterochromatin silencing and nucleosome assembly. The molecular mechanism by which Rtt106p engages in chromatin dynamics remains unclear. Here, we report the 2.5 A crystal structure of the core domain of Rtt106p, which adopts an unusual "double pleckstrin homology" domain architecture that represents a novel structural mode for histone chaperones. A histone H3-H4-binding region and a novel double-stranded DNA-binding region have been identified. Mutagenesis studies reveal that the histone and DNA binding activities of Rtt106p are involved in Sir protein-mediated heterochromatin formation. Our results uncover the structural basis of the diverse functions of Rtt106p and provide new insights into its cellular roles.
Journal of Biological Chemistry 12/2009; 285(6):4251-62. · 4.77 Impact Factor
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ABSTRACT: The homologous RNases RNase E and RNase G are widely distributed in bacteria and function in many important physiological processes, including mRNA degradation, rRNA maturation and so on. In this study, the crystallization and preliminary X-ray analysis of RNase G from Escherichia coli is described. Purified recombinant E. coli RNase G, which has 497 amino acids, was crystallized in the cubic space group F432, with unit-cell parameters a = b = c = 219.84 A. X-ray diffraction data were collected to a resolution of 3.4 A.
Acta Crystallographica Section F Structural Biology and Crystallization Communications 07/2009; 65(Pt 6):586-8. · 0.51 Impact Factor
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ABSTRACT: Human zonula occludens 2 (ZO-2) protein is a multi-domain protein that consists of an SH3 domain, a GK domain and three copies of a PDZ domain with slight divergence. The three PDZ domains act as protein-recognition modules that may mediate protein assembly and subunit localization. The crystal structure of the second PDZ domain of ZO-2 (ZO-2 PDZ2) was determined by molecular replacement at 1.75 A resolution, revealing a dimer in the asymmetric unit. The dimer is stabilized by extensive symmetrical domain-swapping of the beta1 and beta2 strands. Structural comparison shows that the ZO-2 PDZ2 homodimer may have a similar ligand-binding pattern to the ZO-1 PDZ2-connexin 43 complex.
Acta Crystallographica Section F Structural Biology and Crystallization Communications 05/2009; 65(Pt 4):327-30. · 0.51 Impact Factor
