Segregation of nitrogen fixation and oxygenic photosynthesis in the marine cyanobacterium Trichodesmium.
AuthorsBerman-Frank I, Lundgren P, Chen YB, Küpper H, Kolber Z, Bergman B, Falkowski P
JournalScience
PubMed ID11711677
'In the modern ocean, a significant amount of nitrogen fixation is attributed to filamentous, nonheterocystous cyanobacteria of the genus Trichodesmium. In these organisms, nitrogen fixation is confined to the photoperiod and occurs simultaneously with oxygenic photosynthesis. Nitrogenase, the enzyme responsible for biological N2 fixation, is irreversibly inhibited by oxygen in ... More
High density lipoprotein (HDL) particle uptake mediated by scavenger receptor class B type 1 results in selective sorting of HDL cholesterol from protein and polarized cholesterol secretion.
AuthorsSilver DL, Wang N, Xiao X, Tall AR
JournalJ Biol Chem
PubMed ID11301333
'High density lipoprotein (HDL) mediates reverse transport of cholesterol from atheroma foam cells to the liver, but the mechanisms of hepatic uptake and trafficking of HDL particles are poorly understood. In contrast to its accepted role as a cell surface receptor, scavenger receptor class B type 1 (SR-BI) is shown ... More
Acid-induced conformational changes in phosphoglucose isomerase result in its increased cell surface association and deposition on fibronectin fibrils.
AuthorsAmraei M, Jia Z, Reboul P, Nabi IR
JournalJ Biol Chem
PubMed ID12888574
'Phosphoglucose isomerase (PGI) is a glycolytic enzyme that exhibits extracellular cytokine activity as autocrine motility factor, neuroleukin, and maturation factor and that has been recently implicated as an autoantigen in rheumatoid arthritis. In contrast to its receptor-mediated endocytosis at neutral pH, addition of 25 microg/ml of either Alexa 568- or ... More
Serum amyloid A is a ligand for scavenger receptor class B type I and inhibits high density lipoprotein binding and selective lipid uptake.
AuthorsCai L, de Beer MC, de Beer FC, van der Westhuyzen DR
JournalJ Biol Chem
PubMed ID15561721
'Serum amyloid A is an acute phase protein that is carried in the plasma largely as an apolipoprotein of high density lipoprotein (HDL). In this study we investigated whether SAA is a ligand for the HDL receptor, scavenger receptor class B type I (SR-BI), and how SAA may influence SR-BI-mediated ... More
Differences in endocytosis and intracellular sorting of ricin and viscumin in 3T3 cells.
AuthorsMoisenovic M, Tonevitsky A, Agapov I, Niwa H, Schewe H, Bereiter-Hahn J
JournalEur J Cell Biol
PubMed ID12437187
'Ricin and viscumin are heterodimeric protein toxins. Their A-chain is enzymatically active and removes an adenine residue from the 28S rRNA, the B-chain has lectin activity and binds to terminal galactose residues of cell surface receptors. The toxins reveal a high degree of identity in their amino acid sequences. Nevertheless, ... More
Redundant mechanisms recruit actin into the contractile ring in silkworm spermatocytes.
AuthorsChen W, Foss M, Tseng KF, Zhang D,
JournalPLoS Biol
PubMed ID18767903
'Cytokinesis is powered by the contraction of actomyosin filaments within the newly assembled contractile ring. Microtubules are a spindle component that is essential for the induction of cytokinesis. This induction could use central spindle and/or astral microtubules to stimulate cortical contraction around the spindle equator (equatorial stimulation). Alternatively, or in ... More
ECM degradation assays for analyzing local cell invasion.
AuthorsArtym VV, Yamada KM, Mueller SC,
JournalMethods Mol Biol
PubMed ID19247615
'Proteolytic degradation of extracellular matrix (ECM) is a critical step during cell invasion and tissue transmigration that is required for many physiological and pathological processes. Cellular structures that mediate cell adhesion to, degradation of, and invasion into ECM are invadopodia of transformed and tumor cells and podosomes of normal monocytic, ... More
Activation-induced deaminase cloning, localization, and protein extraction from young VH-mutant rabbit appendix.
'Studies in mouse, human, and chicken suggest that activation-induced deaminase (AID) is involved in three known processes leading to antibody diversification: somatic hypermutation, gene conversion, and class-switch recombination. Developing rabbit appendix provides a particularly good site for studying all three of these B cell maturation events. We report here successful ... More
H-type dimer formation of fluorophores: a mechanism for activatable, in vivo optical molecular imaging.
AuthorsOgawa M, Kosaka N, Choyke PL, Kobayashi H,
JournalACS Chem Biol
PubMed ID19480464
'In vivo molecular imaging with target-specific activatable '
Controlling the rates of biochemical reactions and signaling networks by shape and volume changes.
AuthorsLizana L, Bauer B, Orwar O,
JournalProc Natl Acad Sci U S A
PubMed ID18337513
'In biological systems, chemical activity takes place in micrometer- and nanometer-sized compartments that constantly change in shape and volume. These ever-changing cellular compartments embed chemical reactions, and we demonstrate that the rates of such incorporated reactions are directly affected by the ongoing shape reconfigurations. First, we show that the rate ... More
AuthorsSabirsh A, Wetterholm A, Bristulf J, Leffler H, Haeggström JZ, Owman C
JournalJ Lipid Res
PubMed ID15805550
'Leukotriene B4 (LTB4) is a potent lipid mediator of inflammation that acts primarily via a seven-transmembrane-spanning, G-protein-coupled receptor denoted BLT1. Here, we describe the synthesis and characterization of fluorescent analogs of LTB4 that are easy to produce, inexpensive, and without the disadvantages of a radioligand. Fluorescent LTB4 is useful for ... More
Multicolor imaging: the important question of co-localization.
AuthorsSmallcombe A
JournalBiotechniques
PubMed ID11414212
Controlling enzymatic reactions by geometry in a biomimetic nanoscale network.
AuthorsSott K, Lobovkina T, Lizana L, Tokarz M, Bauer B, Konkoli Z, Orwar O
JournalNano Lett
PubMed ID16464036
We demonstrate that a transition from a compact geometry (sphere) to a structured geometry (several spheres connected by nanoconduits) in nanotube-vesicle networks (NVNs) induces an ordinary enzyme-catalyzed reaction to display wavelike properties. The reaction dynamics can be controlled directly by the geometry of the network, and such networks can be ... More
Electrochemical release of fluorescently labeled thiols from patterned gold surfaces.
AuthorsGhaly T, Wildt BE, Searson PC,
JournalLangmuir
PubMed ID19902935
Reductive desorption of alkanethiols is a tool for spatially and temporally controlled release of small molecules or particles from individually addressable gold electrodes. Here we report on the dynamics of release using fluorophore-terminated C6 or C11 thiols. We show that the release kinetics for C6 thiols are determined solely by ... More
A cell-free system for light-dependent nuclear import of phytochrome.
AuthorsPfeiffer A, Kunkel T, Hiltbrunner A, Neuhaus G, Wolf I, Speth V, Adam E, Nagy F, Schäfer E,
JournalPlant J
PubMed ID18980642
Translocation from the cytosol to the nucleus is an essential step in phytochrome (phy) signal transduction. In the case of phytochrome A (phyA), this step occurs with the help of FHY1 (far-red-elongated hypocotyl 1), a specific transport protein. To investigate the components involved in phyA transport, we used a cell-free ... More
Structure and composition of aggregates in two large European rivers, based on confocal laser scanning microscopy and image and statistical analyses.
AuthorsLuef B, Neu TR, Zweimüller I, Peduzzi P,
JournalAppl Environ Microbiol
PubMed ID19633114
Floating riverine aggregates are composed of a complex mixture of inorganic and organic components from their respective aquatic habitats. Their architecture and integrity are supplemented by the presence of extracellular polymeric substances of microbial origin. They are also a habitat for virus-like particles, bacteria, archaea, fungi, algae, and protozoa. In ... More
Alpha4 integrins are type I cAMP-dependent protein kinase-anchoring proteins.
AuthorsLim CJ, Han J, Yousefi N, Ma Y, Amieux PS, McKnight GS, Taylor SS, Ginsberg MH
JournalNat Cell Biol
PubMed ID17369818
A-kinase anchoring proteins (AKAPs) control the localization and substrate specificity of cAMP-dependent protein kinase (PKA), tetramers of regulatory (PKA-R) and catalytic (PKA-C) subunits, by binding to PKA-R subunits. Most mammalian AKAPs bind Type II PKA through PKA-RII (ref. 2), whereas dual specificity AKAPs bind both PKA-RI and PKA-RII (ref. 3). ... More
Dissecting RNA-interference pathway with small molecules.
AuthorsChiu YL, Dinesh CU, Chu CY, Ali A, Brown KM, Cao H, Rana TM
JournalChem Biol
PubMed ID15975509
RNA interference (RNAi) is a process whereby short-interfering RNAs (siRNA) silence gene expression in a sequence-specific manner. We have screened a chemical library of substituted dihydropteridinones and identified a nontoxic, cell permeable, and reversible inhibitor of the RNAi pathway in human cells. Biochemical and fluorescence resonance-energy transfer experiments demonstrated that ... More
Tracking sodium channels in live cells: confocal imaging using fluorescently labeled toxins.
One particularly important class of ion channels in excitable cells are the voltage-dependent sodium channels (VDSC). Knowledge of the distribution of VDSC in living cells is important for studies of neuronal excitability, development, and plasticity. Here, we demonstrate a new method for visualizing the spatial distribution of VDSC in living ... More
SPARC regulates extracellular matrix organization through its modulation of integrin-linked kinase activity.
AuthorsBarker TH, Baneyx G, Cardó-Vila M, Workman GA, Weaver M, Menon PM, Dedhar S, Rempel SA, Arap W, Pasqualini R, Vogel V, Sage EH
JournalJ Biol Chem
PubMed ID16115889
SPARC, a 32-kDa matricellular glycoprotein, mediates interactions between cells and their extracellular matrix, and targeted deletion of Sparc results in compromised extracellular matrix in mice. Fibronectin matrix provides provisional tissue scaffolding during development and wound healing and is essential for the stabilization of mature extracellular matrix. Herein, we report that ... More
Monovalent ligation of the B cell receptor induces receptor activation but fails to promote antigen presentation.
AuthorsKim YM, Pan JY, Korbel GA, Peperzak V, Boes M, Ploegh HL
JournalProc Natl Acad Sci U S A
PubMed ID16492756
We explored the role of antigen valency in B cell receptor (BCR) activation and rearrangement of intracellular MHC class II compartments as factors that contribute to the efficacy of antigen presentation. Using primary B cells that express a hen egg lysozyme (HEL)-specific BCR, we found that oligomeric HEL more efficiently ... More
Recycling of apoprotein E is associated with cholesterol efflux and high density lipoprotein internalization.
AuthorsHeeren J, Grewal T, Laatsch A, Rottke D, Rinninger F, Enrich C, Beisiegel U
JournalJ Biol Chem
PubMed ID12584196
After receptor-mediated endocytosis of triglyceride-rich lipoproteins (TRL) into the liver, TRL particles are immediately disintegrated in peripheral endosomal compartments. Whereas core lipids and apoprotein B are delivered for degradation into lysosomes, TRL-derived apoE is efficiently recycled back to the plasma membrane. This is followed by apoE re-secretion and association of ... More
PlyC: a multimeric bacteriophage lysin.
AuthorsNelson D, Schuch R, Chahales P, Zhu S, Fischetti VA
JournalProc Natl Acad Sci U S A
PubMed ID16818874
Lysins are murein hydrolases produced by bacteriophage that act on the bacterial host cell wall to release progeny phage. When added extrinsically in their purified form, these enzymes produce total lysis of susceptible Gram-positive bacteria within seconds, suggesting a unique antimicrobial strategy. All known Gram-positive lysins are produced as a ... More
High density lipoprotein endocytosis by scavenger receptor SR-BII is clathrin-dependent and requires a carboxyl-terminal dileucine motif.
AuthorsEckhardt ER, Cai L, Shetty S, Zhao Z, Szanto A, Webb NR, Van der Westhuyzen DR
JournalJ Biol Chem
PubMed ID16368683
The high density lipoprotein (HDL) receptor Scavenger Receptor BII (SR-BII) is encoded by an alternatively spliced mRNA from the SR-BI gene and is expressed in various tissues. SR-BII protein differs from SR-BI only in the carboxyl-terminal cytoplasmic tail, which, as we showed previously, must contain a signal that confers predominant ... More
Fluorescence resonance energy transfer analysis of the antagonist- and partial agonist-occupied states of the cholecystokinin receptor.
AuthorsHarikumar KG, Miller LJ
JournalJ Biol Chem
PubMed ID15757907
Changes in receptor conformation are believed to be key for ligand-induced regulation of cellular signaling cascades. However, little information exists about specific conformations of a receptor. We recently applied fluorescence resonance energy transfer to determine distances from distinct points distributed over the surface and within the helical bundle of the ... More
Binding and internalization of lipopolysaccharide by Cla-1, a human orthologue of rodent scavenger receptor B1.
AuthorsVishnyakova TG, Bocharov AV, Baranova IN, Chen Z, Remaley AT, Csako G, Eggerman TL, Patterson AP
JournalJ Biol Chem
PubMed ID12651854
Scavenger receptor, class B, type I (SR-BI) mediates selective uptake of high density lipoprotein (HDL) cholesteryl ester. SR-BI recognizes HDL, low density lipoprotein (LDL), exchangeable apolipoproteins, and protein-free lipid vesicles containing negatively charged phospholipids. Lipopolysaccharides (LPS) are highly glycosylated anionic phospholipids contributing to septic shock. Despite significant structural similarities between ... More
A membrane-proximal basic domain and cysteine cluster in the C-terminal tail of CCR5 constitute a bipartite motif critical for cell surface expression.
AuthorsVenkatesan S, Petrovic A, Locati M, Kim YO, Weissman D, Murphy PM
JournalJ Biol Chem
PubMed ID11514564
We examined the structural requirements for cell surface expression, signaling, and human immunodeficiency virus co-receptor activity for the chemokine receptor, CCR5. Serial C-terminal truncation of CCR5 resulted in progressive loss of cell surface expression; mutants truncated at the 317th position and shorter were not detected at the cell surface. Alanine ... More
Annexin 2 binding to phosphatidylinositol 4,5-bisphosphate on endocytic vesicles is regulated by the stress response pathway.
AuthorsHayes MJ, Merrifield CJ, Shao D, Ayala-Sanmartin J, Schorey CD, Levine TP, Proust J, Curran J, Bailly M, Moss SE
JournalJ Biol Chem
PubMed ID14734570
Annexin 2 is a Ca(2+)-binding protein that has an essential role in actin-dependent macropinosome motility. We show here that macropinosome rocketing can be induced by hyperosmotic shock, either alone or synergistically when combined with phorbol ester or pervanadate. Rocketing was blocked by inhibitors of phosphatidylinositol-3-kinase(s), p38 mitogen-activated protein (MAP) kinase, ... More