Vitellin-binding proteins in the nematode Oscheius tipulae (Nematoda, Rhabditida)

We describe the first application of a non-radioactive ligand-blotting technique to the characterization of proteins interacting with nematode vitellins. Chromatographically purified vitellins from the free-living nematode Oscheius tipulae were labeled with fluorescein in vitro. Ligand-blotting assays with horseradish peroxidase-conjugated anti-fluorescein antibodies showed that labeled vitellins reacted specifically with a polypeptide of approximately 100 kDa, which we named P100. This polypeptide is a specific worm`s vitellin-binding protein that is present only in adult worms. Blots containing purified O. tipulae vitellin preparations showed no detectable signal in the 100 kDa region, ruling out any possibility of yolk polypeptides self-assembling under the conditions used in our assay. Experiments done in the presence of alpha-methyl mannoside ruled out the possibility of vitellins binding to P100 through mannose residues. Triton X-114 fractionation of whole worm extracts showed that P100 is either a membrane protein or has highly hydrophobic regions. (C) 2008 Elsevier Inc. All rights reserved.

Proteins and Peptidases from Conidia and Mycelia of Scedosporium apiospermum Strain HLPB

The conidia-mycelia transformation is an essential step during the life cycle of the fungal human pathogens of the Pseudallescheria boydii complex. In the present study, we have analyzed the protein and peptidase profiles in two distinct morphological stages, conidia and mycelia, of Scedosporium apiospermum sensu stricto. Proteins synthesized by the mycelia, migrating at the ranges of 62-48 and 22-18 kDa, were not detected from the conidial extract. Conidia produced a single cellular peptidase of 28 kDa able to digest copolymerized albumin, while mycelia yielded 6 distinct peptidases ranging from 90 to 28 kDa. All proteolytic enzymes were active at acidic pH and fully inhibited by 1,10-phenanthroline, characterizing these activities as metallo-type peptidases. Quantitative peptidase assay, using soluble albumin, showed a high metallopeptidase production in mycelial cells in comparison with conidia. The regulated expression of proteins and peptidases in different morphological stages of S. apiospermum represents a potential target for isolation of stage-specific markers for biochemical and immunological analysis.

Putative outer membrane proteins of Leptospira interrogans stimulate human umbilical vein endothelial cells (HUVECS) and express during infection

Cell adhesion molecules (CAMs) are surface receptors present in eukaryotic cells that mediate cell-cell or cell-extracellular matrix interactions. Vascular endothelium stimulation in vitro that lead to the upregulation of CAMs was reported for the pathogenic spirochaetes, including rLIC10365 of Leptospira interrogans. In this study, we report the cloning of LIC10507, LIC10508, LIC10509 genes of L interrogans using Escherichia coli as a host system. The rational for selecting these sequences is due to their location in L. interrogans serovar Copenhageni genome that has a potential involvement in pathogenesis. The genes encode for predicted lipoproteins with no assigned functions. The purified recombinant proteins were capable to promote the upregulation of intercellular adhesion molecule 1 (ICAM-1) and E-selectin on monolayers of human umbilical vein endothelial cells (HUVECS). In addition, the coding sequences are expressed in the renal tubules of animal during bacterial experimental infection. The proteins are probably located at the outer membrane of the bacteria since they are detected in detergent-phase of L interrogans Triton X-114 extract. Altogether our data suggest a possible involvement of these proteins during bacterial infection and provide new insights into the role of this region in the pathogenesis of Leptospira. (C) 2008 Elsevier Ltd. All rights reserved.

Percolation in a network with long-range connections: Implications for cytoskeletal structure and function

Cell shape, signaling, and integrity depend on cytoskeletal organization. In this study we describe the cytoskeleton as a simple network of filamentary proteins (links) anchored by complex protein structures (nodes). The structure of this network is regulated by a distance-dependent probability of link formation as P = p/d(s), where p regulates the network density and s controls how fast the probability for link formation decays with node distance (d). It was previously shown that the regulation of the link lengths is crucial for the mechanical behavior of the cells. Here we examined the ability of the two-dimensional network to percolate (i.e. to have end-to-end connectivity), and found that the percolation threshold depends strongly on s. The system undergoes a transition around s = 2. The percolation threshold of networks with s < 2 decreases with increasing system size L, while the percolation threshold for networks with s > 2 converges to a finite value. We speculate that s < 2 may represent a condition in which cells can accommodate deformation while still preserving their mechanical integrity. Additionally, we measured the length distribution of F-actin filaments from publicly available images of a variety of cell types. In agreement with model predictions, cells originating from more deformable tissues show longer F-actin cytoskeletal filaments. (C) 2008 Elsevier B.V. All rights reserved.

Direct Observation of Millisecond to Second Motions in Proteins by Dipolar CODEX NMR Spectroscopy

We present a site-resolved study of stow (ms to s) motions in a protein in the solid (microcrystalline) state performed with the use of a modified version of the centerband-only detection of exchange (CODEX) NMR experiment. CODEX was originally based on measuring changes in molecular orientation by means of the chemical shift anisotropy (CSA) tensor, and in our modification, angular reorientations of internuclear vectors are observed. The experiment was applied to the study of stow (15)N-(1)H motions of the SH3 domain of chicken a-spectrin. The protein was perdeuterated with partial back-exchange of protons at labile sites. This allowed indirect (proton) detection of (15)N nuclei and thus a significant enhancement of sensitivity. The diluted proton system also made negligible proton-driven spin diffusion between (15)N nuclei, which interferes with the molecular exchange (motion) and hampers the acquisition of dynamic parameters. The experiment has shown that approximately half of the peaks in the 2D (15)N-(1)H correlation spectrum exhibit exchange in a different extent. The correlation time of the slow motion for most peaks is 1 to 3 s. This is the first NMR study of the internal dynamics of proteins in the solid state on the millisecond to second time scale with site-specific spectral resolution that provides both time-scale and geometry information about molecular motions.

SBTX, a new toxic protein distinct from soyatoxin and other toxic soybean [Glycine max] proteins, and its inhibitory effect on Cercospora sojina growth

SBTX, a novel toxin from soybean, was purified by ammonium sulfate fractionation followed by chromatographic steps DEAE-Cellulose, CM-Sepharose and Superdex 200 HR fast-protein liquid chromatography (FPLC). Lethality of SBTX to mice (LD50 5.6 mg/kg) was used as parameter in the purification steps. SBTX is a 44-kDa basic glycoprotein composed of two polypeptide chains (27 and 17 kDa) linked by a disulfide bond. The N-terminal sequences of the 44 and 27 kDa chains were identical (ADPTFGFTPLGLSEKANLQIMKAYD), differing from that of 17 kDa (PNPKVFFDMTIGGQSAGRIVMEEYA). SBTX contains high levels of Glx, Ala, Asx, Gly and Lys and showed maximum absorption at 280 nm, epsilon(1 cm) (1%) of 6.3, and fluorescence emission in the 290-450nm range upon excitation at 280nm. The secondary structure content was 35% alpha-helix, 13% beta-strand and beta-sheet, 27% beta-turn, 25% unordered, and 1% aromatic residues. Immunological assays showed that SBTX was related to other toxic proteins, such as soyatoxin and canatoxin, and cross-reacted weekly with soybean trypsin inhibitor and agglutinin, but it was devoid of protease-inhibitory and hemagglutinating activities. The inhibitory effect of SBTX on growth of Cercospora sojina, fungus causing frogeye leaf spot in soybeans, was observed at 50 mu g/ml, concentration 112 times lesser than that found to be lethal to mice. This effect on phytopathogenic fungus is a potential attribute for the development of transgenic plants with enhanced resistance to pathogens. (c) 2007 Elsevier Ltd. All rights reserved.

Mapping the Intramolecular Vibrational Energy Flow in Proteins Reveals Functionally Important Residues

Unveiling the mechanisms of energy relaxation in biomolecules is key to our understanding of protein stability, allostery, intramolecular signaling, and long-lasting quantum coherence phenomena at ambient temperatures. Yet, the relationship between the pathways of energy transfer and the functional role of the residues involved remains largely unknown. Here, we develop a simulation method of mapping out residues that are highly efficient in relaxing an initially localized excess vibrational energy and perform site-directed mutagenesis functional assays to assess the relevance of these residues to protein function. We use the ligand binding domains of thyroid hormone receptor (TR) subtypes as a test case and find that conserved arginines, which are critical to TR transactivation function, are the most effective heat diffusers across the protein structure. These results suggest a hitherto unsuspected connection between a residue`s ability to mediate intramolecular vibrational energy redistribution and its functional relevance.

Molecular characterization of Arabidopsis thaliana PUF proteins - binding specificity and target candidates

PUF proteins regulate both stability and translation through sequence-specific binding to the 3` UTR of target mRNA transcripts. Binding is mediated by a conserved PUF domain, which contains eight repeats of approximately 36 amino acids each. Found in all eukaryotes, they have been related to several developmental processes. Analysis of the 25 Arabidopsis Pumilio (APUM) proteins presenting PUF repeats reveals that 12 (APUM-1 to APUM-12) have a PUF domain with 50-75% similarity to the Drosophila PUF domain. Through three-hybrid assays, we show that APUM-1 to APUM-6 can bind specifically to the Nanos response element sequence recognized by Drosophila Pumilio. Using an Arabidopsis RNA library in a three-hybrid screening, we were able to identify an APUM-binding consensus sequence. Computational analysis allowed us to identify the APUM-binding element within the 3` UTR in many Arabidopsis transcripts, even in important mRNAs related to shoot stem cell maintenance. We demonstrate that APUM-1 to APUM-6 are able to bind specifically to APUM-binding elements in the 3` UTR of WUSCHEL, CLAVATA-1, PINHEAD/ZWILLE and FASCIATA-2 transcripts. The results obtained in the present study indicate that the APUM proteins may act as regulators in Arabidopsis through an evolutionarily conserved mechanism, which may open up a new approach for investigating mRNA regulation in plants.

Expression of genes encoding cytosolic and endoplasmic reticulum HSP90 proteins in the aquatic fungus Blastocladiella emersonii

HSP90 proteins are important molecular chaperones involved in multiple cellular processes. This work reports the characterization of cDNAs encoding two distinct HSP90 proteins (named HSP90A and HSP90B) from the chytridiomycete Blastocladiella emersonii. Deduced amino acid sequences of HSP90A and HSP90B exhibit signatures of the cytosolic and endoplasmic reticulum (ER) HSP90 proteins, respectively. A genomic clone encoding HSP90A was also characterized indicating the presence of a single intron of 184 bp interrupting the coding region, located near the amino-terminus of the protein. Expression of both HSP90A and HSP90B genes increases significantly during heat shock at 38 degrees C, with highest induction ratios observed in cells stressed during germination of the fungus. Changes in the amount of HSP90A transcript were also evaluated during B. emersonii life cycle at physiological temperature (27 degrees C), and its levels were found to increase both during germination and sporulation of the fungus. HSP90A protein levels were analyzed during B. emersonii life cycle and significant changes were observed only during sporulation. Furthermore, during heat stress a large increase in the amount of HSP90A protein was observed. Induction of HSP90A and HSP90B genes during heat stress indicates the importance of both genes in the response to high temperature in B. emersonii. (C) 2008 Elsevier B.V. All rights reserved.

Characterization of a beta-1,3-glucanase active in the alkaline midgut of Spodoptera frugiperda larvae and its relation to beta-glucan-binding proteins

Spodoptera frugiperda beta-1,3-glucanase (SLam) was purified from larval midgut. It has a molecular mass of 37.5 kDa, an alkaline optimum pH of 9.0, is active against beta-1,3-glucan (laminarin), but cannot hydrolyze yeast beta-1,3-1,6-glucan or other polysaccharides. The enzyme is an endoglucanase with low processivity (0.4), and is not inhibited by high concentrations of substrate. In contrast to other digestive beta-1,3-glucanases from insects, SLam is unable to lyse Saccharomyces cerevisae cells. The cDNA encoding SLam was cloned and sequenced, showing that the protein belongs to glycosyl hydrolase family 16 as other insect glucanases and glucan-binding proteins. Multiple sequence alignment of beta-1,3-glucanases and beta-glucan-binding protein supports the assumption that the beta-1,3-glucanase gene duplicated in the ancestor of mollusks and arthropods. One copy originated the derived beta-1,3-glucanases by the loss of an extended N-terminal region and the beta-glucan-binding proteins by the loss of the catalytic residues. SLam homology modeling suggests that E228 may affect the ionization of the catalytic residues, thus displacing the enzyme pH optimum. SLam antiserum reacts with a single protein in the insect midgut. Immunocytolocalization shows that the enzyme is present in secretory vesicles and glycocalyx from columnar cells. (C) 2010 Elsevier Ltd. All rights reserved.

The Xanthomonas citri effector protein PthA interacts with citrus proteins involved in nuclear transport, protein folding and ubiquitination associated with DNA repair

P>Xanthomonas axonopodis pv. citri utilizes the type III effector protein PthA to modulate host transcription to promote citrus canker. PthA proteins belong to the AvrBs3/PthA family and carry a domain comprising tandem repeats of 34 amino acids that mediates protein-protein and protein-DNA interactions. We show here that variants of PthAs from a single bacterial strain localize to the nucleus of plant cells and form homo- and heterodimers through the association of their repeat regions. We hypothesize that the PthA variants might also interact with distinct host targets. Here, in addition to the interaction with alpha-importin, known to mediate the nuclear import of AvrBs3, we describe new interactions of PthAs with citrus proteins involved in protein folding and K63-linked ubiquitination. PthAs 2 and 3 preferentially interact with a citrus cyclophilin (Cyp) and with TDX, a tetratricopeptide domain-containing thioredoxin. In addition, PthAs 2 and 3, but not 1 and 4, interact with the ubiquitin-conjugating enzyme complex formed by Ubc13 and ubiquitin-conjugating enzyme variant (Uev), required for K63-linked ubiquitination and DNA repair. We show that Cyp, TDX and Uev interact with each other, and that Cyp and Uev localize to the nucleus of plant cells. Furthermore, the citrus Ubc13 and Uev proteins complement the DNA repair phenotype of the yeast Delta ubc13 and Delta mms2/uev1a mutants, strongly indicating that they are also involved in K63-linked ubiquitination and DNA repair. Notably, PthA 2 affects the growth of yeast cells in the presence of a DNA damage agent, suggesting that it inhibits K63-linked ubiquitination required for DNA repair.

Cell-cell signal-dependent dynamic interactions between HD-GYP and GGDEF domain proteins mediate virulence in Xanthomonas campestris

RpfG is a paradigm for a class of widespread bacterial two-component regulators with a CheY-like receiver domain attached to a histidine-aspartic acid-glycine-tyrosine-proline (HD-GYP) cyclic di-GMP phosphodiesterase domain. In the plant pathogen Xanthomonas campestris pv. campestris (Xcc), a two-component system comprising RpfG and the complex sensor kinase RpfC is implicated in sensing and responding to the diffusible signaling factor (DSF), which is essential for cell-cell signaling. RpfF is involved in synthesizing DSF, and mutations of rpfF, rpfG, or rpfC lead to a coordinate reduction in the synthesis of virulence factors such as extracellular enzymes, biofilm structure, and motility. Using yeast two-hybrid analysis and fluorescence resonance energy transfer experiments in Xcc, we show that the physical interaction of RpfG with two proteins with diguanylate cyclase (GGDEF) domains controls a subset of RpfG-regulated virulence functions. RpfG interactions were abolished by alanine substitutions of the three residues of the conserved GYP motif in the HD-GYP domain. Changing the GYP motif or deletion of the two GGDEF-domain proteins reduced Xcc motility but not the synthesis of extracellular enzymes or biofilm formation. RpfG-GGDEF interactions are dynamic and depend on DSF signaling, being reduced in the rpfF mutant but restored by DSF addition. The results are consistent with a model in which DSF signal transduction controlling motility depends on a highly regulated, dynamic interaction of proteins that influence the localized expression of cyclic di-GMP.

Picosecond Dynamics of the Prototropic Reactions of 7-Hydroxyflavylium Photoacids Anchored at an Anionic Micellar Surface

Three water-insoluble, micelle-anchored flavylium salts, 7-hydroxy-3-octyl-flavylium chloride, 4`-hexyl-7-hydroxyflavylium chloride, and 6-hexyl-7-hydroxy-4-methyl-flavylium chloride, have been employed to probe excited-state prototropic reactions in micellar sodium dodecyl sulfate (SDS). In SDS micelles, the fluorescence decays of these three flavylium salts are tetraexponential functions in the pH range from 1.0 to 4.6 at temperatures from 293 to 318 K. The four components of the decays are assigned to Four kinetically coupled excited species in the micelle: specifically, promptly deprotonable (AH(+)*) and nonpromptly deprotonable (AH(h)(+)*) orientations of the acid in the micelle. the base-proton geminate pair (A*center dot center dot center dot H(+)), and the free conjugate base (A*). The initial prompt deprotonation to form the germinate pair occurs at essentially the same rate (k(d) similar to 6-7 x 10(10) s(-1)) for all three photoacids. Recombination of the germinate pair is similar to 3-fold faster than the rate of proton escape from the pair (k(rec) similar to 3 x 10(10) s(-1) and k(diss) similar to 1 x 10(10) s(-1)), corresponding to an intrinsic recombination efficiency of the pair of similar to 75%. Finally, the reprotonation of the short-lived free A* (200-350 ps, depending oil the photoacid) has two components, only one of which depends oil the proton concentration in the intermicellar aqueous phase. Ultrafast transfer of the proton to water and substantial compartmentalization of the photogenerated proton at the micelle surface Oil the picosecond time scale strongly suggest preferential transfer of the proton to preformed hydrogen-bonded water bridges between the photoacid and the anionic headgroups. This localizes the proton in the vicinity of the excited base much more efficiently than ill bulk water, resulting ill the predominance of geminate re reprotonation at the micelle surface.

Optimization of the rheological properties of probiotic yoghurts supplemented with milk proteins

This study aimed to optimize the rheological properties of probiotic yoghurts supplemented with skimmed milk powder (SMP) whey protein concentrate (WPC) and sodium caseinate (Na-Cn) by using an experimental design type simplex-centroid for mixture modeling It Included seven batches/trials three were supplemented with each type of the dairy protein used three corresponding to the binary mixtures and one to the ternary one in order to increase protein concentration in 1 g 100 g(-1) of final product A control experiment was prepared without supplementing the milk base Processed milk bases were fermented at 42 C until pH 4 5 by using a starter culture blend that consisted of Streptococcus thermophilus Lactobacillus delbrueckii subsp bulgaricus and Bifidobacterium (Humans subsp lactis The kinetics of acidification was followed during the fermentation period as well the physico-chemical analyses enumeration of viable bacteria and theological characteristics of the yoghurts Models were adjusted to the results (kinetic responses counts of viable bacteria and theological parameters) through three regression models (linear quadratic and cubic special) applied to mixtures The results showed that the addition of milk proteins affected slightly acidification profile and counts of S thermophilus and B animal`s subsp lactis but it was significant for L delbrueckii subsp bulgaricus Partially-replacing SMP (45 g/100 g) with WPC or Na-Cn simultaneously enhanced the theological properties of probiotic yoghurts taking into account the kinetics of acidification and enumeration of viable bacteria (C) 2010 Elsevier Ltd All rights reserved

Identification of non-zein proteins in BR473 maize protein bodies by LC-nanoESI-MS/MS

The nutritional value of maize seed is limited due to its high content of storage proteins (zeins), which are deficient in essential amino acids such as lysine and tryptophan. In a previous paper, we showed that protein bodies obtained from BR473 maize variety, developed by Embrapa (Brazilian Agricultural Research Corporation), were mainly constituted by Z27 and a smaller quantity of Z50 gamma-zeins. Besides zein proteins, other not identified protein band in the SDS/PAGE was also observed, which could indicate the presence of non-zein proteins additionally to gamma-zeins. In the present paper, we have demonstrated the presence of non-zein proteins in BR473 maize protein bodies by LC-nanoESI-MS/MS and database searching. This fact could be related to the excellent energetic value and higher protein quality of BR473 maize grains, since high lysine concentration in some maize varieties has been related to the presence of cytoskeleton proteins that are non-zeins. We have identified the following proteins: Brittle-1 protein (chloroplast precursor), Legumin-1, glyceroldehyde-3-phosphate dehydrogenase, and elongation factor 1-alpha.