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Helix Domain (helix + domain)
Selected AbstractsProtein kinase A RII-like (R2D2) proteins exhibit differential localization and AKAP interaction,CYTOSKELETON, Issue 7 2008Amy E. Hanlon Newell Abstract A-kinase anchoring proteins (AKAPs) bind to protein kinase A (PKA) via an amphipathic helix domain that interacts with a dimerization/docking domain on the regulatory (R) subunit of PKA. Four other mammalian proteins (ROPN1, ASP, SP17, and CABYR) also contain a highly conserved RII dimerization/docking (R2D2) domain, suggesting all four proteins may interact with all AKAPs in a manner similar to RII. All four of these proteins were originally detected in the flagellum of mammalian sperm. In this report, we demonstrate that all four R2D2 proteins are expressed in a wide variety of tissues and three of the proteins SP17, CABYR, and ASP are located in motile cilia of human bronchus and fallopian tubes. In addition, we detect SP17 in primary cilia. We also provide evidence that ROPN1 and ASP bind to a variety of AKAPs and this interaction can be disrupted with anchoring inhibitor peptides. The interaction of SP17 and CABYR with AKAPs appears to be much more limited. None of the R2D2 proteins appears to bind cAMP, a fundamental characteristic of the regulatory subunits of PKA. These observations suggest that R2D2 proteins utilize docking interactions with AKAPs to accomplish their function of regulating cilia and flagella. Based on location, affinity for AKAPs and lack of affinity for cAMP, it appears that each R2D2 protein has a unique role in this process. Cell Motil. Cytoskeleton 2008. © 2008 Wiley-Liss, Inc. [source] Autophosphorylation of Archaeoglobus fulgidus Rio2 and crystal structures of its nucleotide,metal ion complexesFEBS JOURNAL, Issue 11 2005Nicole LaRonde-LeBlanc The highly conserved, atypical RIO serine protein kinases are found in all organisms, from archaea to man. In yeast, the kinase activity of Rio2 is necessary for the final processing step of maturing the 18S ribosomal rRNA. We have previously shown that the Rio2 protein from Archaeoglobus fulgidus contains both a small kinase domain and an N-terminal winged helix domain. Previously solved structures using crystals soaked in nucleotides and Mg2+ or Mn2+ showed bound nucleotide but no ordered metal ions, leading us to the conclusion that they did not represent an active conformation of the enzyme. To determine the functional form of Rio2, we crystallized it after incubation with ATP or ADP and Mn2+. Co-crystal structures of Rio2,ATP,Mn and Rio2,ADP,Mn were solved at 1.84 and 1.75 Å resolution, respectively. The ,-phosphate of ATP is firmly positioned in a manner clearly distinct from its location in canonical serine kinases. Comparison of the Rio2,ATP,Mn complex with the Rio2 structure with no added nucleotides and with the ADP complex indicates that a flexible portion of the Rio2 molecule becomes ordered through direct interaction between His126 and the ,-phosphate oxygen of ATP. Phosphopeptide mapping of the autophosphorylation site of Rio2 identified Ser128, within the flexible loop and directly adjacent to the part that becomes ordered in response to ATP, as the target. These results give us further information about the nature of the active site of Rio2 kinase and suggest a mechanism of regulation of its enzymatic activity. [source] Solution structure of the region 51,160 of human KIN17 reveals an atypical winged helix domainPROTEIN SCIENCE, Issue 12 2007Ludovic Carlier Abstract Human KIN17 is a 45-kDa eukaryotic DNA- and RNA-binding protein that plays an important role in nuclear metabolism and in particular in the general response to genotoxics. Its amino acids sequence contains a zinc finger motif (residues 28,50) within a 30-kDa N-terminal region conserved from yeast to human, and a 15-kDa C-terminal tandem of SH3-like subdomains (residues 268,393) only found in higher eukaryotes. Here we report the solution structure of the region 51,160 of human KIN17. We show that this fragment folds into a three-,-helix bundle packed against a three-stranded ,-sheet. It belongs to the winged helix (WH) family. Structural comparison with analogous WH domains reveals that KIN17 WH module presents an additional and highly conserved 310 -helix. Moreover, KIN17 WH helix H3 is not positively charged as in classical DNA-binding WH domains. Thus, human KIN17 region 51,160 might rather be involved in protein,protein interaction through its conserved surface centered on the 310 -helix. [source] Crystal structure of 3-hydroxyanthranilic acid 3,4-dioxygenase from Saccharomyces cerevisiae: A special subgroup of the type III extradiol dioxygenasesPROTEIN SCIENCE, Issue 4 2006Xiaowu Li Abstract 3-Hydroxyanthranilic acid 3,4-dioxygenase (3HAO) is a non-heme ferrous extradiol dioxygenase in the kynurenine pathway from tryptophan. It catalyzes the conversion of 3-hydroxyanthranilate (HAA) to quinolinic acid (QUIN), an endogenous neurotoxin, via the activation of N-methyl-D-aspartate (NMDA) receptors and the precursor of NAD+ biosynthesis. The crystal structure of 3HAO from S. cerevisiae at 2.4 Å resolution shows it to be a member of the functionally diverse cupin superfamily. The structure represents the first eukaryotic 3HAO to be resolved. The enzyme forms homodimers, with two nickel binding sites per molecule. One of the bound nickel atoms occupies the proposed ferrous-coordinated active site, which is located in a conserved double-strand ,-helix domain. Examination of the structure reveals the participation of a series of residues in catalysis different from other extradiol dioxygenases. Together with two iron-binding residues (His49 and Glu55), Asp120, Asn51, Glu111, and Arg114 form a hydrogen-bonding network; this hydrogen-bond network is key to the catalysis of 3HAO. Residues Arg101, Gln59, and the substrate-binding hydrophobic pocket are crucial for substrate specificity. Structure comparison with 3HAO from Ralstonia metallidurans reveals similarities at the active site and suggests the same catalytic mechanism in prokaryotic and eukaryotic 3HAO. Based on sequence comparison, we suggest that bicupin of human 3HAO is the first example of evolution from a monocupin dimer to bicupin monomer in the diverse cupin superfamilies. Based on the model of the substrate HAA at the active site of Y3HAO, we propose a mechanism of catalysis for 3HAO. [source] Structure of the thioredoxin-fold domain of human phosducin-like protein 2ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 2 2009Xiaochu Lou Human phosducin-like protein 2 (hPDCL2) has been identified as belonging to subgroup II of the phosducin (Pdc) family. The members of this family share an N-terminal helix domain and a C-terminal thioredoxin-fold (Trx-fold) domain. The X-ray crystal structure of the Trx-fold domain of hPDCL2 was solved at 2.70,Å resolution and resembled the Trx-fold domain of rat phosducin. Comparative structural analysis revealed the structural basis of their putative functional divergence. [source] Crystallization and X-ray diffraction analysis of an all-RNA U39C mutant of the minimal hairpin ribozymeACTA CRYSTALLOGRAPHICA SECTION D, Issue 1 2003Valerie Grum-Tokars The hairpin ribozyme is a naturally occurring catalytic RNA composed of two helix,loop,helix domains, A and B, that dock to form the biologically active enzyme. Previously, the crystal structure of the hairpin has been solved as a four-way helical junction that incorporated the U1A protein as an artificial crystal-packing motif [Rupert & Ferré-D'Amaré (2001), Nature (London), 410, 780,786]. Here, the crystallization of a minimal junctionless hairpin ribozyme 64-mer is reported in the absence of protein. Crystals grow in space group P6122, with unit-cell parameters a = 93.1, c = 123.2,Å. Complete diffraction data have been collected to 3.35,Å resolution. Structural analysis should provide details of intermolecular RNA docking, including the ground-state conformations of the U39C mutation relevant to hairpin catalysis. [source] | ||||||||||