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Articles 1 - 15 of 15

Full-Text Articles in Biochemistry, Biophysics, and Structural Biology

Rac/Rop Gtpases And Auxin Signaling, H. Wu, O. Hazak, Alice Cheung, S. Yalovsky Apr 2011

Rac/Rop Gtpases And Auxin Signaling, H. Wu, O. Hazak, Alice Cheung, S. Yalovsky

Alice Cheung

Auxin functions as a key morphogen in regulating plant growth and development. Studies on auxin-regulated gene expression and on the mechanism of polar auxin transport and its asymmetric distribution within tissues have provided the basis for realizing the molecular mechanisms underlying auxin function. In eukaryotes, members of the Ras and Rho subfamilies of the Ras superfamily of small GTPases function as molecular switches in many signaling cascades that regulate growth and development. Plants do not have Ras proteins, but they contain Rho-like small G proteins called RACs or ROPs that, like fungal and metazoan Rhos, are regulators of cell polarity ...


Pollen Tubes Lacking A Pair Of K+ Transporters Fail To Target Ovules In Arabidopsis, Y. Lu, S. Chanroj, L. Zulkifli, M. Johnson, N. Uozumi, Alice Cheung, H. Sze Jan 2011

Pollen Tubes Lacking A Pair Of K+ Transporters Fail To Target Ovules In Arabidopsis, Y. Lu, S. Chanroj, L. Zulkifli, M. Johnson, N. Uozumi, Alice Cheung, H. Sze

Alice Cheung

Flowering plant reproduction requires precise delivery of the sperm cells to the ovule by a pollen tube. Guidance signals from female cells are being identified; however, how pollen responds to those cues is largely unknown. Here, we show that two predicted cation/proton exchangers (CHX) in Arabidopsis thaliana, CHX21 and CHX23, are essential for pollen tube guidance. Male fertility was unchanged in single chx21 or chx23 mutants. However, fertility was impaired in chx21 chx23 double mutant pollen. Wild-type pistils pollinated with a limited number of single and double mutant pollen producing 62% fewer seeds than those pollinated with chx23 single ...


The Sv40 Late Protein Vp4 Is A Viroporin That Forms Pores To Disrupt Membranes For Viral Release, Smita Raghava, Kristen Giorda, F. Romano, Alejandro Heuck, Daniel Hebert Jan 2011

The Sv40 Late Protein Vp4 Is A Viroporin That Forms Pores To Disrupt Membranes For Viral Release, Smita Raghava, Kristen Giorda, F. Romano, Alejandro Heuck, Daniel Hebert

Alejandro P. Heuck

Nonenveloped viruses are generally released by the timely lysis of the host cell by a poorly understood process. For the nonenveloped virus SV40, virions assemble in the nucleus and then must be released from the host cell without being encapsulated by cellular membranes. This process appears to involve the well-controlled insertion of viral proteins into host cellular membranes rendering them permeable to large molecules. VP4 is a newly identified SV40 gene product that is expressed at late times during the viral life cycle that corresponds to the time of cell lysis. To investigate the role of this late expressed protein ...


An Interdomain Sector Mediating Allostery In Hsp70 Molecular Chaperones, Robert Smock, Olivier Rivoire, William Russ, Joanna Swain, Stanislas Leibler, Rama Ranganathan, Lila Gierasch Sep 2010

An Interdomain Sector Mediating Allostery In Hsp70 Molecular Chaperones, Robert Smock, Olivier Rivoire, William Russ, Joanna Swain, Stanislas Leibler, Rama Ranganathan, Lila Gierasch

Lila Gierasch

Allosteric coupling between protein domains is fundamental to many cellular processes. For example, Hsp70 molecular chaperones use ATP binding by their actin-like N-terminal ATPase domain to control substrate interactions in their C-terminal substrate-binding domain, a reaction that is critical for protein folding in cells. Here, we generalize the statistical coupling analysis to simultaneously evaluate co-evolution between protein residues and functional divergence between sequences in protein sub-families. Applying this method in the Hsp70/110 protein family, we identify a sparse but structurally contiguous group of co-evolving residues called a ‘sector’, which is an attribute of the allosteric Hsp70 sub-family that links ...


Systematic Discovery Of Regulatory Motifs In Fusarium Graminearum By Comparing Four Fusarium Genomes, Lokesh Kumar, Andrew Breakspear, Corby Kistler, Li-Jun Ma, Xiaohui Xie Mar 2010

Systematic Discovery Of Regulatory Motifs In Fusarium Graminearum By Comparing Four Fusarium Genomes, Lokesh Kumar, Andrew Breakspear, Corby Kistler, Li-Jun Ma, Xiaohui Xie

Li-Jun Ma

Background

Fusarium graminearum (Fg), a major fungal pathogen of cultivated cereals, is responsible for billions of dollars in agriculture losses. There is a growing interest in understanding the transcriptional regulation of this organism, especially the regulation of genes underlying its pathogenicity. The generation of whole genome sequence assemblies for Fg and three closely related Fusarium species provides a unique opportunity for such a study.

Results

Applying comparative genomics approaches, we developed a computational pipeline to systematically discover evolutionarily conserved regulatory motifs in the promoter, downstream and the intronic regions of Fg genes, based on the multiple alignments of sequenced Fusarium ...


Toc Receptor Dimerization Participates In The Initiation Of Membrane Translocation During Protein Import Into Chloroplasts, Jeonghwa Lee, Fei Wang Wang, Danny Schnell Nov 2009

Toc Receptor Dimerization Participates In The Initiation Of Membrane Translocation During Protein Import Into Chloroplasts, Jeonghwa Lee, Fei Wang Wang, Danny Schnell

Danny Schnell

The post-translational import of nucleus-encoded preproteins into chloroplasts occurs through multimeric translocons in the outer (Toc) and inner (Tic) membranes. The high fidelity of the protein import process is maintained by specific recognition of the transit peptide of preproteins by the coordinate activities of two homologous GTPase Toc receptors, Toc34 and Toc159. Structural and biochemical studies suggest that dimerization of the Toc receptors functions as a component of the mechanism to control access of preproteins to the membrane translocation channel of the translocon. We show that specific mutations that disrupted receptor dimerization in vitro reduced the rate of protein import ...


A Toc159 Import Receptor Mutant, Defective In Hydrolysis Of Gtp, Supports Preprotein Import Into Chloroplasts, Birgit Agne, Sibylle Infanger, Fei Wang, Valère Hofstetter, Gwendoline Rahim, Meryll Martin, Dong Wook Lee, Inhwan Hwang, Danny Schnell, Felix Kessler Mar 2009

A Toc159 Import Receptor Mutant, Defective In Hydrolysis Of Gtp, Supports Preprotein Import Into Chloroplasts, Birgit Agne, Sibylle Infanger, Fei Wang, Valère Hofstetter, Gwendoline Rahim, Meryll Martin, Dong Wook Lee, Inhwan Hwang, Danny Schnell, Felix Kessler

Danny Schnell

The heterotrimeric Toc core complex of the chloroplast protein import apparatus contains two GTPases, Toc159 and Toc34, together with the protein-conducting channel Toc75. Toc159 and Toc34 are exposed at the chloroplast surface and function in preprotein recognition. Together, they have been shown to facilitate the import of photosynthetic proteins into chloroplasts in Arabidopsis. Consequently, the ppi2 mutant lacking atToc159 has a non-photosynthetic albino phenotype. Previous mutations in the conserved G1 and G3 GTPase motifs abolished the function of Toc159 in vivo by disrupting targeting of the receptor to chloroplasts. Here, we demonstrate that a mutant in a conserved G1 lysine ...


A Comprehensive Structure–Function Analysis Of Arabidopsis Sni1 Defines Essential Regions And Transcriptional Repressor Activity, Rebecca Mosher, Wendy Durrant, Dong Wang, Jungi Song, Xinnian Dong Jul 2006

A Comprehensive Structure–Function Analysis Of Arabidopsis Sni1 Defines Essential Regions And Transcriptional Repressor Activity, Rebecca Mosher, Wendy Durrant, Dong Wang, Jungi Song, Xinnian Dong

Dong Wang

The expression of systemic acquired resistance (SAR) in plants involves the upregulation of many Pathogenesis-Related (PR) genes, which work in concert to confer resistance to a broad spectrum of pathogens. Because SAR is a costly process, SAR-associated transcription must be tightly regulated. Arabidopsis thaliana SNI1 (for Suppressor of NPR1, Inducible) is a negative regulator of SAR required to dampen the basal expression of PR genes. Whole genome transcriptional profiling showed that in the sni1 mutant, Nonexpresser of PR genes (NPR1)–dependent benzothiadiazole S-methylester–responsive genes were specifically derepressed. Interestingly, SNI1 also repressed transcription when expressed in yeast, suggesting that it ...


The Arabidopsis Atr1 Myb Transcription Factor Controls Indolic Glucosinolate Homeostasis, John Celenza, Juan Quiel, Gromoslaw Smolen, Houra Merrikh, Angela Silvestro, Jennifer Normanly, Judith Bender Jan 2005

The Arabidopsis Atr1 Myb Transcription Factor Controls Indolic Glucosinolate Homeostasis, John Celenza, Juan Quiel, Gromoslaw Smolen, Houra Merrikh, Angela Silvestro, Jennifer Normanly, Judith Bender

Jennifer Normanly

Plants derive a number of important secondary metabolites from the amino acid tryptophan (Trp), including the growth regulator indole-3-acetic acid (IAA) and defense compounds against pathogens and herbivores. In previous work, we found that a dominant overexpression allele of the Arabidopsis (Arabidopsis thaliana) Myb transcription factor ATR1, atr1D, activates expression of a Trp synthesis gene as well as the Trp-metabolizing genes CYP79B2, CYP79B3, and CYP83B1, which encode enzymes implicated in production of IAA and indolic glucosinolate (IG) antiherbivore compounds. Here, we show that ATR1 over expression confers elevated levels of IAA and IGs. In addition, we show that an atr1 ...


Overexpression Of An Arabidopsis Formin Stimulates Supernumerary Actin Cable Formation From Pollen Tube Cell Membrane, Alice Cheung, H. Wu Jan 2004

Overexpression Of An Arabidopsis Formin Stimulates Supernumerary Actin Cable Formation From Pollen Tube Cell Membrane, Alice Cheung, H. Wu

Alice Cheung

Formins, actin-nucleating proteins that stimulate the de novo polymerization of actin filaments, are important for diverse cellular and developmental processes, especially those dependent on polarity establishment. A subset of plant formins, referred to as group I, is distinct from formins from other species in having evolved a unique N-terminal structure with a signal peptide, a Pro-rich, potentially glycosylated extracellular domain, and a transmembrane domain. We show here that overexpression of the Arabidopsis formin AFH1 in pollen tubes induces the formation of arrays of actin cables that project into the cytoplasm from the cell membrane and that its N-terminal structure targets ...


Dependence Of Endoplasmic Reticulum-Associated Degradation On The Peptide Binding Domain And Concentration Of Bip, Mehdi Kabani, Stephanie Kelley, Michael Morrow, Diana Montgomery, Renuka Sivendran, Mark Rose, Lila Gierasch, Jeffrey Brodsky Mar 2003

Dependence Of Endoplasmic Reticulum-Associated Degradation On The Peptide Binding Domain And Concentration Of Bip, Mehdi Kabani, Stephanie Kelley, Michael Morrow, Diana Montgomery, Renuka Sivendran, Mark Rose, Lila Gierasch, Jeffrey Brodsky

Lila Gierasch

ER-associated degradation (ERAD) removes defective and mis-folded proteins from the eukaryotic secretory pathway, but mutations in the ER lumenal Hsp70, BiP/Kar2p, compromise ERAD efficiency in yeast. Because attenuation of ERAD activates the UPR, we screened for kar2 mutants in which the unfolded protein response (UPR) was induced in order to better define how BiP facilitates ERAD. Among the kar2 mutants isolated we identified the ERAD-specific kar2-1 allele (Brodsky et al. J. Biol. Chem. 274, 3453–3460). The kar2-1 mutation resides in the peptide-binding domain of BiP and decreases BiP's affinity for a peptide substrate. Peptide-stimulated ATPase activity was ...


Trp-Dependent Auxin Biosynthesis In Arabidopsis: Involvement Of Cytochrome P450s Cyp79b2 And Cyp79b3, Yunde Zhao, Anna Hull, Neeru Gupta, Kendrick Goss, José Alonso, Joseph Ecker, Jennifer Normanly, Joanne Chory, John Celenza Jan 2002

Trp-Dependent Auxin Biosynthesis In Arabidopsis: Involvement Of Cytochrome P450s Cyp79b2 And Cyp79b3, Yunde Zhao, Anna Hull, Neeru Gupta, Kendrick Goss, José Alonso, Joseph Ecker, Jennifer Normanly, Joanne Chory, John Celenza

Jennifer Normanly

The plant hormone auxin regulates many aspects of plant growth and development. Although several auxin biosynthetic pathways have been proposed, none of these pathways has been precisely defined at the molecular level. Here we provide in planta evidence that the two Arabidopsis cytochrome P450s, CYP79B2 and CYP79B3, which convert tryptophan (Trp) to indole-3-acetaldoxime (IAOx) in vitro, are critical enzymes in auxin biosynthesis in vivo. IAOx is thus implicated as an important intermediate in auxin biosynthesis. Plants overexpressing CYP79B2 contain elevated levels of free auxin and display auxin overproduction phenotypes. Conversely, cyp79B2 cyp79B3 double mutants have reduced levels of IAA and ...


The Ldl Receptor Clustering Motif Interacts With The Clathrin Terminal Domain In A Reverse Turn Conformation., Richard Kibbey, Josep Rizo, Lila Gierasch, Richard Anderson Jul 1998

The Ldl Receptor Clustering Motif Interacts With The Clathrin Terminal Domain In A Reverse Turn Conformation., Richard Kibbey, Josep Rizo, Lila Gierasch, Richard Anderson

Lila Gierasch

Previously the hexapeptide motif FXNPXY807 in the cytoplasmic tail of the LDL receptor was shown to be essential for clustering in clathrin-coated pits. We used nuclear magnetic resonance line-broadening and transferred nuclear Overhauser effect measurements to identify the molecule in the clathrin lattice that interacts with this hexapeptide, and determined the structure of the bound motif. The wild-type peptide bound in a single conformation with a reverse turn at residues NPVY. Tyr807Ser, a peptide that harbors a mutation that disrupts receptor clustering, displayed markedly reduced interactions. Clustering motif peptides interacted with clathrin cages assembled in the presence or absence of ...


Effect Of Charged Residue Substitutions On The Membrane-Interactive Properties Of Signal Sequences Of The Escherichia Coli Lamb Protein., Jeffrey Jones, Lila Gierasch Oct 1994

Effect Of Charged Residue Substitutions On The Membrane-Interactive Properties Of Signal Sequences Of The Escherichia Coli Lamb Protein., Jeffrey Jones, Lila Gierasch

Lila Gierasch

Although the central role of the signal sequence in protein export is well established, the molecular details underlying signal sequence in vivo function remain unclear. As part of our continuing effort to relate signal sequence phenotypes to specific biophysical properties, we have carried out an extensive characterization of the secondary structure and lipid interactions for a family of peptides corresponding to the wild-type E. coli LamB signal sequence, and mutants that harbor charged residue point mutations in the hydrophobic core region. We used membrane-resident fluorescence quenching according to the parallax method to determine the relative depth of insertion of tryptophan-labeled ...


Reorganization Of Lipid Domain Structure In Membranes By A Transmembrane Peptide: An Esr Spin Label Study On The Effect Of The Escherichia Coli Outer Membrane Protein A Signal Peptide On The Fluid Lipid Domain Connectivity In Binary Mixtures Of Dimyristoyl Phosphatidylcholine And Distearoyl Phosphatidylcholine., M. Sankaram, D. Marsh, Lila Gierasch, T. Thompson Jun 1994

Reorganization Of Lipid Domain Structure In Membranes By A Transmembrane Peptide: An Esr Spin Label Study On The Effect Of The Escherichia Coli Outer Membrane Protein A Signal Peptide On The Fluid Lipid Domain Connectivity In Binary Mixtures Of Dimyristoyl Phosphatidylcholine And Distearoyl Phosphatidylcholine., M. Sankaram, D. Marsh, Lila Gierasch, T. Thompson

Lila Gierasch

The effect of a transmembrane peptide on the domain structure of a two-component, two-phase lipid bilayer composed of dimyristoyl phosphatidylcholine (DMPC) and distearoyl phosphatidylcholine (DSPC) was examined by spin label electron spin resonance (ESR) spectroscopy. The peptide, pOmpA, is the hydrophobic, 25-residue signal sequence of the outer membrane protein A from Escherichia coli. Nitroxide derivatives of the phospholipid DSPC, 16-DSPCSL, and of the pOmpA signal peptide, pOmpA-IASL, were used as probes. The first-derivative lineshapes of the ESR spectra were analyzed using a normalized intensity ratio, R, that gives information on the average sizes of the disconnected fluid domains and their ...