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PubMed2002

Analytical reproducibility in (1)H NMR-based metabonomic urinalysis.

Metabonomic analysis of biofluids and tissues utilizing high-resolution NMR spectroscopy and chemometric techniques has proven valuable in characterizing the biochemical response to toxicity for many xenobiotics. To assess the analytical reproducibility of metabonomic protocols, sample preparation and NMR data acquisition were performed at two sites (one using a 500 MHz and the other using a 600 MHz system) using two identical (split) sets of urine samples from an 8-day acute study of hydrazine toxicity in the rat. Despite the difference in spectrometer operating frequency, both datasets were extremely similar when analyzed using principal components analysis (PCA) and gave near-identical descriptions of the metabolic responses to hydrazine treatment. The main consistent difference between the datasets was related to the efficiency of water resonance suppression in the spectra. In a 4-PC model of both datasets combined, describing all systematic dose- and time-related variation (88% of the total variation), differences between the two datasets accounted for only 3% of the total modeled variance compared to ca. 15% for normal physiological (pre-dose) variation. Furthermore, <3% of spectra displayed distinct inter-site differences, and these were clearly identified as outliers in their respective dose-group PCA models. No samples produced clear outliers in both datasets, suggesting that the outliers observed did not reflect an unusual sample composition, but rather sporadic differences in sample preparation leading to, for example, very dilute samples. Estimations of the relative concentrations of citrate, hippurate, and taurine were in >95% correlation (r(2)) between sites, with an analytical error comparable to normal physiological variation in concentration (4-8%). The excellent analytical reproducibility and robustness of metabonomic techniques demonstrated here are highly competitive compared to the best proteomic analyses and are in significant contrast to genomic microarray platforms, both of which are complementary techniques for predictive and mechanistic toxicology. These results have implications for the quantitative interpretation of metabonomic data, and the establishment of quality control criteria for both regulatory agencies and for integrating data obtained at different sites.

Animals↗
PubMed2006

What makes species unique? The contribution of proteins with obscure features.

BACKGROUND: Proteins with obscure features (POFs), which lack currently defined motifs or domains, represent between 18% and 38% of a typical eukaryotic proteome. To evaluate the contribution of this class of proteins to the diversity of eukaryotes, we performed a comparative analysis of the predicted proteomes derived from 10 different sequenced genomes, including budding and fission yeast, worm, fly, mosquito, Arabidopsis, rice, mouse, rat, and human. RESULTS: Only 1,650 protein groups were found to be conserved among these proteomes (BLAST E-value threshold of 10(-6)). Of these, only three were designated as POFs. Surprisingly, we found that, on average, 60% of the POFs identified in these 10 proteomes (44,236 in total) were species specific. In contrast, only 7.5% of the proteins with defined features (PDFs) were species specific (17,554 in total). As a group, POFs appear similar to PDFs in their relative contribution to biological functions, as indicated by their expression, participation in protein-protein interactions and association with mutant phenotypes. However, POF have more predicted disordered structure than PDFs, implying that they may exhibit preferential involvement in species-specific regulatory and signaling networks. CONCLUSION: Because the majority of eukaryotic POFs are not well conserved, and by definition do not have defined domains or motifs upon which to formulate a functional working hypothesis, understanding their biochemical and biological functions will require species-specific investigations.

Animals↗
PubMed2005

Representations of molecular pathways: an evaluation of SBML, PSI MI and BioPAX.

MOTIVATION: Analysis and simulation of pathway data is of high importance in bioinformatics. Standards for representation of information about pathways are necessary for integration and analysis of data from various sources. Recently, a number of representation formats for pathway data, SBML, PSI MI and BioPAX, have been proposed. RESULTS: In this paper we compare these formats and evaluate them with respect to their underlying models, information content and possibilities for easy creation of tools. The evaluation shows that the main structure of the formats is similar. However, SBML is tuned towards simulation models of molecular pathways while PSI MI is more suitable for representing details about particular interactions and experiments. BioPAX is the most general and expressive of the formats. These differences are apparent in allowed information and the structure for representation of interactions. We discuss the impact of these differences both with respect to information content in existing databases and computational properties for import and analysis of data.

Computational Biology↗
PubMed2003

Genetic modification removes an immunodominant allergen from soybean.

The increasing use of soybean (Glycine max) products in processed foods poses a potential threat to soybean-sensitive food-allergic individuals. In vitro assays on soybean seed proteins with sera from soybean-sensitive individuals have immunoglobulin E reactivity to abundant storage proteins and a few less-abundant seed proteins. One of these low abundance proteins, Gly m Bd 30 K, also referred to as P34, is in fact a major (i.e. immunodominant) soybean allergen. Although a member of the papain protease superfamily, Gly m Bd 30 K has a glycine in the conserved catalytic cysteine position found in all other cysteine proteases. Transgene-induced gene silencing was used to prevent the accumulation of Gly m Bd 30 K protein in soybean seeds. The Gly m Bd 30 K-silenced plants and their seeds lacked any compositional, developmental, structural, or ultrastructural phenotypic differences when compared with control plants. Proteomic analysis of extracts from transgenic seed detected the suppression of Gly m Bd 30 K-related peptides but no other significant changes in polypeptide pattern. The lack of a collateral alteration of any other seed protein in the Gly m Bd 30 K-silenced seeds supports the presumption that the protein does not have a role in seed protein processing and maturation. These data provide evidence for substantial equivalence of composition of transgenic and non-transgenic seed eliminating one of the dominant allergens of soybean seeds.

Allergens↗
PubMed2026

Quantitative proteomic profiling of neural cells-specific metabolic reprogramming in response to mitochondrial dysfunction using iMPAQT2.

Age-related mitochondrial dysfunction is increasingly recognized as a key contributor to neurodegenerative disease pathogenesis. In the central nervous system, neurons, oligodendrocytes, and astrocytes which derived from neural stem cells, fulfill distinct metabolic and functional roles. However, the specific vulnerabilities of these cell types to mitochondrial impairment remain unclear. In this study, we employed the iMPAQT2 proteomics platform to systematically compare the metabolic profiles of neurons, oligodendrocytes, and astrocytes, and to elucidate the molecular consequences of mitochondrial dysfunction induced by chloramphenicol and oligomycin. Our findings indicate that neurons and oligodendrocytes primarily rely on oxidative phosphorylation (OXPHOS) for ATP production, whereas astrocytes predominantly utilize glycolysis. It is noteworthy that oligodendrocytes exhibited enriched pathways for cholesterol synthesis, fatty acid degradation, and heme catabolism-processes that are critical for myelin maintenance. Treatment with the mitochondrial function inhibitors chloramphenicol or oligomycin reduced the expression of OXPHOS enzymes in all cell types. This reduction was particularly pronounced in oligodendrocytes for glycolysis, cholesterol synthesis, heme degradation, and fatty acid degradation. These results suggest that oligodendrocytes are particularly vulnerable to mitochondrial dysfunction, which may play a pivotal role in the pathogenesis of age-related neurodegenerative disorders.

Animals↗
PubMed2006

Towards second-generation proteome analysis of murine enamel-forming cells.

Proteome analysis of rat enamel-forming cells, initiated over a decade ago, has provided valuable insights to enamel biology. In preparation for a more comprehensive, second-generation proteomic exploration, we evaluated an updated microsample-profiling strategy that comprises sequential extraction of enamel epithelium, parallel one- and two-dimensional gel electrophoresis, and mass spectrometric sequence analysis. The results indicated that several hundred proteins, representing various cellular compartments (including membranes), are amenable to identification with a starting tissue volume of <10 microl. With its increased proteomic depth and breadth, this straightforward approach constitutes a major advance from the first-generation work (10-fold increased proteome coverage), although care was needed to ensure a comparably high stringency of protein identification. Expression proteomics has an exciting potential to elucidate the inner workings of murine enamel epithelial cells, leading to an improved understanding of enamel in health and disease.

Ameloblasts↗
PubMed2026

Insights into the mechanism of enhanced tetramethylpyrazine production in dehulled adlay fermented by Bacillus subtilis BJ3-2.

Tetramethylpyrazine (TTMP) is a vital bioactive alkaloid and characteristic flavor compound in fermented foods. Our previous study found that fermentation of adlay by Bacillus subtilis BJ3-2 efficiently accumulates TTMP, whereas the underlying high-yield mechanism remains unclear. This study investigated the fermentation characteristics, gene transcription and protein expression of B. subtilis BJ3-2 in dehulled adlay (BDA) and soybean (BSB), respectively, and elucidated the mechanism responsible for high-yield TTMP production. The results showed that glutamate, leucine and phenylalanine were major free amino acids in BDA. The TTMP yield in BDA at 48&#xa0;h (6.11&#xa0;mg/g dry weight) was 360-fold higher than that in BSB. Transcriptomic and proteomic analysis demonstrated that compared with the soybean substrate, dehulled adlay substrate significantly up-regulated the expression of alsSD and ilvBH genes and their encoding proteins in B. subtilis BJ3-2, which were involved in C5-branched dibasic acid metabolism, 2-oxocarboxylic acid metabolism, and valine, leucine and isoleucine biosynthesis. Meanwhile, acetoin degradation was inhibited by down-regulating acetoin dehydrogenase complex (acoABCL) in citrate cycle, glycolysis/gluconeogenesis and carbon metabolism. Additionally, nitrogen metabolism pathway was transcriptionally enhanced to guarantee sufficient ammonium supply. Notably, protein-protein interaction and molecular docking analyses revealed that acetohydroxyacid synthase (ilvBH) interacted tightly with &#x3b1;-acetolactate decarboxylase (alsD), potentially forming a metabolic channel for acetoin synthesis. In conclusion, the efficient synthesis of TTMP in BDA was primarily attributed to the high synthesis and low degradation of acetoin, and the moderate synthesis of ammonium/ammonia. This study provided a theoretical basis for the targeted and efficient biosynthesis of TTMP.

Bacillus subtilis↗
PubMed2006

Technologies for bacterial surface proteomics.

Proteins from bacterial membranes are notoriously difficult to analyze using the traditional technologies encompassed under the term 'proteomics'. This is because of several factors, including the comparatively low abundance of most membrane proteins within a complex mixture containing cytoplasmic metabolic enzymes, the poor solubility of membrane components such as phospholipids, lipopolysaccharides and peptidoglycans, and the inherent hydrophobicity of many integral membrane proteins that contain up to 15 transmembrane-spanning regions. Recent advances in gel-based and chromatographic separations, coupled with protein and peptide labelling and the exquisite sensitivity of mass spectrometry, are finally beginning to overcome these problems. New technologies in membrane proteomics enable comparative analysis of these recalcitrant proteins from bacteria under a variety of biological conditions.

Bacteria↗
PubMed2001

Combined transcriptome and proteome analysis as a powerful approach to study genes under glucose repression in Bacillus subtilis.

We used 2D protein gel electrophoresis and DNA microarray technologies to systematically analyze genes under glucose repression in B:acillus subtilis. In particular, we focused on genes expressed after the shift from glycolytic to gluconeogenic at the middle logarithmic phase of growth in a nutrient sporulation medium, which remained repressed by the addition of glucose. We also examined whether or not glucose repression of these genes was mediated by CcpA, the catabolite control protein of this bacterium. The wild-type and ccpA1 cells were grown with and without glucose, and their proteomes and transcriptomes were compared. 2D gel electrophoresis allowed us to identify 11 proteins, the synthesis of which was under glucose repression. Of these proteins, the synthesis of four (IolA, I, S and PckA) was under CcpA-independent control. Microarray analysis enabled us to detect 66 glucose-repressive genes, 22 of which (glmS, acoA, C, yisS, speD, gapB, pckA, yvdR, yxeF, iolA, B, C, D, E, F, G, H, I, J, R, S and yxbF ) were at least partially under CcpA-independent control. Furthermore, we found that CcpA and IolR, a repressor of the iol divergon, were involved in the glucose repression of the synthesis of inositol dehydrogenase encoded by iolG included in the above list. The CcpA-independent glucose repression of the iol genes appeared to be explained by inducer exclusion.

Amino Acid Sequence↗
PubMed2003

A comprehensive whole genome bacterial phylogeny using correlated peptide motifs defined in a high dimensional vector space.

As whole genome sequences continue to expand in number and complexity, effective methods for comparing and categorizing both genes and species represented within extremely large datasets are required. Methods introduced to date have generally utilized incomplete and likely insufficient subsets of the available data. We have developed an accurate and efficient method for producing robust gene and species phylogenies using very large whole genome protein datasets. This method relies on multidimensional protein vector definitions supplied by the singular value decomposition (SVD) of a large sparse data matrix in which each protein is uniquely represented as a vector of overlapping tetrapeptide frequencies. Quantitative pairwise estimates of species similarity were obtained by summing the protein vectors to form species vectors, then determining the cosines of the angles between species vectors. Evolutionary trees produced using this method confirmed many accepted prokaryotic relationships. However, several unconventional relationships were also noted. In addition, we demonstrate that many of the SVD-derived right basis vectors represent particular conserved protein families, while many of the corresponding left basis vectors describe conserved motifs within these families as sets of correlated peptides (copeps). This analysis represents the most detailed simultaneous comparison of prokaryotic genes and species available to date.

Amino Acid Motifs↗
PubMed2005

Comparative genomics on nemo-like kinase gene.

WNT signals are transduced to the planar cell polarity (PCP) pathway or the beta-catenin pathway. Drosophila Frizzled (Fz), Starry night (Stan), Van Gogh (Vang), Dishevelled (Dsh), Prickle (Pk), Diego (Dgo) and Nemo (Nmo) are implicated in the PCP signaling pathway. Choi and Benzer identified Drosophila Nmo in 1994, and Brott et al identified mouse Nemo-like kinase (Nlk) in 1998. Nlk positively regulates the PCP pathway, and negatively regulates the beta-catenin pathway. Here, we identified and characterized rat Nlk gene, Nlk2 gene and Nlkp pseudogene by using bioinformatics. Nlk gene, consisting of 11 exons, was mapped to rat chromosome 10q25. Rat Nlk gene encoded 515-aa Nlk protein with the serine/threonine kinase domain, poly(His) tracts and poly(Ala) tract, which showed 100, 99.8, 97.1 and 89.5% total-amino-acid identity with mouse Nlk, human NLK, Xenopus nlk and zebrafish nlk, respectively. Rat Nlk2 gene and Nlkp pseudogene were mapped to rat chromosome 13p13 and 2q44, respectively. Nlk2 gene and Nlkp pseudogene, consisting of a single exon, were not evolutionarily conserved. Nlk2 gene and Nlkp pseudogene were predicted as retrotransposed Nlk homologs within the rat genome. Nlk2 gene encoded a 480-aa Nlk2 protein with partial deletion within the kinase domain, which was predicted as the dominant negative Nlk homolog. This is the first report on the Nlk gene and retrotransposed Nlk homologs within the rat genome.

Amino Acid Sequence↗
PubMed2006

Cleavage of endoplasmic reticulum proteins in hepatocellular carcinoma: Detection of generated fragments in patient sera.

BACKGROUND & AIMS: In the past decade, there has been a rising incidence of hepatocellular carcinoma (HCC) and a progressive increase in HCC-related mortality in the United States and Western Europe. The poor survival of patients with HCC is largely related to the lack of reliable tools for early diagnosis. METHODS: We have applied proteomics tools to the comparative analysis of protein profiles between HCC and adjacent nontumor tissues as a means for discovering novel molecular markers. RESULTS: Forty-seven protein spots that showed reproducible variation were identified by mass spectrometry, corresponding to 23 distinct genes. A positive correlation between transcript and protein level variations was observed for only 7 out of the 23 genes. Proteolytic cleavage accounted for the discrepancies between messenger RNA and protein level changes for 7 genes including calreticulin, PDIA3, PDI, and GRP78. We detected a fragment of each of these 4 endoplasmic reticulum proteins in the culture supernatant of the PLC-PRF5 hepatoma cell line, suggesting that their cleavage leads to release of selected cleaved products in the extracellular compartment. We also detected calreticulin and PDIA3 cleavage products in sera of patients with HCC. A statistically highly significant difference in calreticulin and PDIA3 fragment serum levels between patients with HCC and healthy individuals was observed. Amounts of calreticulin and PDIA3 fragments were also significantly different between patients with HCC and at-risk patients (patients with chronic hepatitis or cirrhosis). CONCLUSIONS: Specific isoforms in general and cleavage products in particular should therefore be further evaluated as new markers for HCC.

Biomarkers, Tumor↗
PubMed2005

Quantitative proteomics analysis of differential protein expression and oxidative modification of specific proteins in the brains of old mice.

The brain is susceptible to oxidative stress, which is associated with age-related brain dysfunction, because of its high content of peroxidizable unsaturated fatty acids, high oxygen consumption per unit weight, high content of key components for oxidative damage, and the relative scarcity of antioxidant defense systems. Protein oxidation, which results in functional disruption, is not random but appears to be associated with increased oxidation in specific proteins. By using a proteomics approach, we have compared the protein levels and specific protein carbonyl levels, an index of oxidative damage in the brains of old mice, to these parameters in the brains of young mice and have identified specific proteins that are altered as a function of aging. We show here that the expression levels of dihydropyrimidinase-like 2 (DRP2), alpha-enolase (ENO1), dynamin-1 (DNM1), and lactate dehydrogenase 2 (LDH2) were significantly increased in the brains of old versus young mice; the expression levels of three unidentified proteins were significantly decreased. The specific carbonyl levels of beta-actin (ACTB), glutamine synthase (GS), and neurofilament 66 (NF-66) as well as a novel protein were significantly increased, indicating protein oxidation, in the brains of old versus young mice. These results were validated by immunochemistry. In addition, enzyme activity assays demonstrated that oxidation was associated with decreased GS activity, while the activity of lactate dehydrogenase was unchanged in spite of an up-regulation of LDH2 levels. Several of the up-regulated and oxidized proteins in the brains of old mice identified in this report are known to be oxidized in neurodegenerative diseases as well, suggesting that these proteins may be particularly susceptible to processes associated with neurodegeneration. Our results establish an initial basis for understanding protein alterations that may lead to age-related cellular dysfunction in the brain.

Actins↗
PubMed2001

The wheat-grain proteome as a basis for more efficient cultivar identification.

The wheat-grain proteome was investigated, as a basis for devising more efficient methods of cultivar identification or discrimination. Australian wheats (Halberd, Cranbrook, CD87 and Katepwa) were used as the basis of this study. These cultivars were selected on the basis of differences in the quality types represented, in terms of dough-processing attributes that can suit one cultivar better than another for specific types of industrial utilisation. Total wheat endosperm (flour) protein extracts were prepared from mature wheat for two-dimensional electrophoresis, across both acidic (pH 4-7) and basic (pH 6-11) pH ranges. Three particular regions of the proteome maps were chosen for close comparison, involving two sets of gluten proteins and a nongluten protein region (involving small heat shock proteins), based on previous protein characterisation. Differences in the nongluten protein regions (heat shock proteins and other unidentified polypeptides) are of particular interest as being possible targets for use in developing new approaches to cultivar discrimination, such as the development of simple immunoassays.

Electrophoresis, Gel, Two-Dimensional↗
PubMed2006

Analysis of protein-protein interactions with a multi-capillary electrophoresis instrument.

Protein-protein interactions were analyzed by zone electrophoresis of premixed equilibrium mixtures of a fluorescence-labeled protein at a constant concentration and unlabeled protein at a variety of concentrations using a 96-CE instrument equipped with a LIF detector. The interactions between labeled-con A versus succinylated ovalbumin, labeled-trypsin versus four proteinaceous trypsin inhibitors and labeled-insulin versus seven anti-insulin monoclonal antibodies were analyzed using a dual buffer system, in which a 60 mM borate-Na buffer (pH 9.35) was used as electrophoresis buffer and 60 mM MOPS-Na (pH 7.35) containing 0.1% Tween 20 was used as a sample buffer. The dual buffer system allowed fast and reproducible analyses of interactions at a physiological pH using uncoated fused-silica capillaries. The change in the mobility moment, the first statistical moment of an electropherogram on the mobility axis (Shimura, K., Uchiyama, N., Enomoto, M., Matsumoto, H., Kasai, K., Anal. Chem. 2005, 77, 564-572), of the labeled proteins were analyzed as a function of the concentration of unlabeled proteins. The dissociation constants for seven antibodies ranging from sub nanomolar to micromolar was determined based on the results of one cycle of parallel electrophoresis runs, which completed in 30 min using 20 pmol (120 ng) of labeled insulin and 5 pmol (750 ng) each of the mAb.

Animals↗
PubMed2003

Proteomic changes in Escherichia coli TG1 after metabolic engineering for enhanced trichloroethene biodegradation.

Through metabolic engineering, new enzymatic pathways can be introduced into cells to enable or enhance production or biotransformation of chemicals. However, these changes have physiological consequences that can be important but are not well understood. Here we describe the use of two-dimensional gel electrophoresis (2-DE) to detect changes in the proteome of Escherichia coli cells that have been engineered to transform the pollutant trichloroethene (TCE) with the enzyme toluene o-monooxygenase (TOM). Comparison of 2-DE gels (isoelectric point range 4-7) for E. coli cells with and without the ability to synthesize TOM revealed 31 new proteins in TOM-containing cells as well as nine proteins not detected in those cells but present in the plasmid control strain. Exposure of TOM-containing cells to TCE led to the synthesis of four new proteins and the loss of only one protein. Thus, this example of metabolic engineering has a substantial and complex impact on the physiology of these cells that was clearly revealed using a proteomic approach.

Bacterial Proteins↗
PubMed2004

Has the yo-yo stopped? An assessment of human protein-coding gene number.

Since the identification of approximately 25,000 proteins from the draft human genome assembly in 2001, estimates of the total have oscillated between 30,000 and 70,000. The recently announced genome closure has not generated a consensus gene count despite this being a key parameter for many areas of biology including drug target discovery and characterization of the human proteome. Contrary to earlier predictions of constitutive under-detection for eukaryotic genes, the latest model organism updates have produced minor increases in the worm but fly and yeast gene numbers have decreased. The postdraft, precompletion interval has produced large increases in human transcript coverage, continuous improvements in genome assembly and refinements in automated genomic annotation. Notably these enhancements have resulted in an Ensembl human protein-coding gene number of 22,184, a decrease of 1862 since the first release. Longitudinal database surveys indicate that redundancy-reduced human mRNA and protein collections are flattening out at approximately 28,000, although Ensembl maps approximately 20,000 known sequences. Observations suggest high-throughput cloning projects are predominantly extending known genes or sampling new splice forms and novel protein discovery has slowed to a trickle. The hypothesis that substantial numbers of short proteins remain experimentally and computationally undetected in mammalian genomes is neither supported by sequence data nor by the extensive homology between mouse and human proteins. Aggregating the independent annotations for complete transcripts from seven completed human chromosomes extrapolates to approximately 25,000 genes. The inclusion of partial putative genes would increase this to above 30,000 but recent data suggest these represent predominantly nonprotein-coding transcripts. Mass spectrometry-based proteomics has already verified more than 10% of human genes but has not identified significant numbers of unpredicted proteins. The available data are thus converging to a basal protein-coding gene number well below 30,000, which could even be as low as 25,000.

Chromosomes, Human↗
PubMed2005

Two-dimensional fluorescence difference gel electrophoresis analysis of the urine proteome in human diabetic nephropathy.

Urinary proteins may provide clues regarding pathogenesis of kidney disease as well as providing markers of disease activity. We employed two-dimensional differential in-gel electrophoretic analysis (2-D DIGE) to assess multiple urine samples in patients with diabetic nephropathy. Patient samples were collected as timed overnight collections. All the patients had longstanding diabetes, impaired renal function, and overt proteinuria. Control and patient urinary protein were analyzed by 2-D DIGE and DeCyder analysis. Ninety-nine spots were significantly regulated in the urine proteome of the diabetic samples, with 63 up- and 36 down-regulated. One spot corresponding to a pI 5-6 and a molecular weight between 45 and 66 kDa was consistently up-regulated by 19-fold across individuals in the diabetic group. Surface-enhanced laser desorption/ionization-time of flight analysis of in-gel tryptic digest of this spot identified this protein as alpha 1 antitrypsin (AAT). ELISA of urine samples from a separate group of patients and controls confirmed a marked increase of AAT in diabetic patients. Immunostaining of human diabetic kidneys revealed up-regulation of AAT in areas of renal fibrosis. In conclusion, we developed a method to analyze numerous urine samples from patients and allowed for detection and identification of regulated urine protein spots.

Aged↗