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Protein Complex Formation (protein + complex_formation)

Distribution by Scientific Domains

Life Sciences	75%

Selected Abstracts

Transcription factor binding study by capillary zone electrophoretic mobility shift assay

ELECTROPHORESIS, Issue 1-2 2003
Zsolt Ronai
Abstract Regulation of gene expression through interaction of proteins with specific DNA sequences is a central issue in functional genomics. Capillary electrophoretic mobility shift assay is an efficient novel method for the investigation of sequence specific protein-DNA interactions, allowing rapid and sensitive quantification of the complex formation. In this paper, we present a pilot study on capillary zone electrophoretic mobility shift assay (CZEMSA) to investigate the interaction between the transcription factors of HeLa nuclear extract and Sp1-specific fluorescein-labeled oligonucleotide, using the unlabeled probe as competitor. The mobility shift assay was accomplished by CZE in coated capillaries without polymeric buffer additives. Specificity of the DNA protein complex formation was verified by competition experiments, as well as by supershift assay with an anti-Sp1 antibody. The applied electric field strength did not affect the stability of DNA-protein complex during the electrophoretic analysis, allowing rapid identification and quantification of the protein DNA interaction. A practical application to study the interaction between Oryza sativa MADS-box transcription factor 4 (OsMADS4) and its consensus sequence is also reported. [source]

Two different Pseudomonas aeruginosa chemosensory signal transduction complexes localize to cell poles and form and remould in stationary phase

MOLECULAR MICROBIOLOGY, Issue 1 2006
Zehra Tüzün Güvener
Summary Pseudomonas aeruginosa has sets of sensory genes designated che and che2. The che genes are required for flagella-mediated chemotaxis. The che2 genes are expressed in the stationary phase of growth and are probably also involved in flagella,mediated behavioural responses. P. aeruginosa also has 26 chemoreceptor genes, six of which are preferentially expressed in stationary phase. Subcellular localization experiments indicated that Che proteins form signal transduction complexes at cell poles throughout growth. Cyan fluorescent protein (CFP)-tagged McpA, a stationary phase-expressed chemoreceptor, appeared and colocalized with yellow fluorescent protein (YFP)-tagged CheA when cells entered stationary phase. This indicates that P. aeruginosa chemotaxis protein complexes are subject to remoulding by chemoreceptor proteins that are expressed when cells stop growing. CheA-CFP and CheY2-YFP tagged proteins that were coexpressed in the same cell had separate subcellular locations, indicating that Che2 proteins do not enter into direct physical interactions with Che proteins. Che2 protein complex formation required McpB, another stationary phase induced chemoreceptor that is predicted to be soluble. This implies that Che2 complexes have a function that depends on just one chemoreceptor. Our results suggest that motile P. aeruginosa cells have signal transduction systems that are adapted to allow non-growing cells to sense and respond to their environment differently from actively growing cells. [source]

Visualization of protein interactions in living plant cells using bimolecular fluorescence complementation

THE PLANT JOURNAL, Issue 3 2004
Michael Walter
Summary Dynamic networks of protein,protein interactions regulate numerous cellular processes and determine the ability to respond appropriately to environmental stimuli. However, the investigation of protein complex formation in living plant cells by methods such as fluorescence resonance energy transfer has remained experimentally difficult, time consuming and requires sophisticated technical equipment. Here, we report the implementation of a bimolecular fluorescence complementation (BiFC) technique for visualization of protein,protein interactions in plant cells. This approach relies on the formation of a fluorescent complex by two non-fluorescent fragments of the yellow fluorescent protein brought together by association of interacting proteins fused to these fragments (Hu et al., 2002). To enable BiFC analyses in plant cells, we generated different complementary sets of expression vectors, which enable protein interaction studies in transiently or stably transformed cells. These vectors were used to investigate and visualize homodimerization of the basic leucine zipper (bZIP) transcription factor bZIP63 and the zinc finger protein lesion simulating disease 1 (LSD1) from Arabidopsis as well as the dimer formation of the tobacco 14-3-3 protein T14-3c. The interaction analyses of these model proteins established the feasibility of BiFC analyses for efficient visualization of structurally distinct proteins in different cellular compartments. Our investigations revealed a remarkable signal fluorescence intensity of interacting protein complexes as well as a high reproducibility and technical simplicity of the method in different plant systems. Consequently, the BiFC approach should significantly facilitate the visualization of the subcellular sites of protein interactions under conditions that closely reflect the normal physiological environment. [source]

Amyloid , protein toxicity mediated by the formation of amyloid-, protein precursor complexes

ANNALS OF NEUROLOGY, Issue 6 2003
Daniel C. Lu MD
The amyloid-, protein precursor, a type 1 transmembrane protein, gives rise to the amyloid ,-protein, a neurotoxic peptide postulated to be involved in the pathogenesis of Alzheimer's disease. Here, we show that soluble amyloid , protein accelerates amyloid precursor protein complex formation, a process that contributes to neuronal cell death. The mechanism of cell death involves the recruitment of caspase-8 to the complex, followed by intracytoplasmic caspase cleavage of amyloid precursor protein. In vivo, the levels of soluble amyloid , protein correlated with caspase-cleaved fragments of the amyloid precursor protein in brains of Alzheimer's disease subjects. These findings suggest that soluble amyloid , protein,induced multimerization of the amyloid precursor protein may be another mechanism by which amyloid , protein contributes to synapse loss and neuronal cell death seen in Alzheimer's disease. Ann Neurol 2003;54:781,789 [source]