Biomedical subjects

Birgit Kersten

Publications and source records attributed to Birgit Kersten.

9 recordsLinked to original sources

PubMed2007

Generation of plant protein microarrays and investigation of antigen-antibody interactions.

The application of proteomics methods, such as the protein microarray technology, in plant science has been strongly supported by the completion of genome sequencing projects of Arabidopsis thaliana and rice. In this chapter we describe a method to generate plant protein microarrays and to use them for characterizing monoclonal antibodies or polyclonal sera with regard to their specificity and cross-reactivity. The method starts with characterized E. coli cDNA expression clones encoding His-tagged plant proteins. After expression and purification of these recombinant proteins in high throughput, protein microarrays are generated utilizing a contact printer. For the detection of the recombinant proteins on the microarrays, an anti-RGS-His6 antibody is used. To characterize specific antibodies, the microarrays are incubated with the respective antibody solutions followed by fluorescently labeled secondary antibodies. Signal detection is performed by means of an arrayscanner system. Protein microarrays containing the whole proteome of a plant will represent the ideal format to test antibody specificity and cross-reactivity in the future.

Antibody Specificity↗

PubMed2007

Phosphorylation studies using plant protein microarrays.

Identifying protein kinase substrates is one major focus of protein kinase research and supports the elucidation of signal transduction pathways and their complex regulation. In this chapter we describe a protein microarray-based in vitro method, which permits a systematic screening of immobilized proteins for their phosphorylation by specific protein kinases. This high-throughput method allows the identification of potential kinase substrates. The method starts with plant protein microarrays containing hundreds of purified recombinant His-tagged proteins. The microarrays have to be incubated with the soluble and active kinase in the presence of radioactive [gamma33-P]ATP. Only small volumes of active kinase are needed for one microarray experiment. Radioactive signals are then detectable by phosphor imager or X-ray film. The identified potential substrates have to be verified by other in vitro or in vivo methods, as both the kinase and the substrate may not interact with each other under in vivo conditions. This screening method could be generally applicable for direct identification of candidate substrates of various protein kinases.

Arabidopsis↗

PubMed2006

Plant phosphoproteomics: a long road ahead.

Phosphoproteomics can be defined as the comprehensive study of protein phosphorylation by identification of the phosphoproteins, exact mapping of the phosphorylation sites, quantification of phosphorylation, and eventually, revealing their biological function. Its place in today's research is vitally important to address the most fundamental question - how the phosphorylation events control most, if not all, of the cellular processes in a given organism? Despite the immense importance of phosphorylation, the analysis of phosphoproteins on a proteome-wide scale remains a formidable challenge. Nevertheless, several technologies have been developed, mostly in yeast and mammals, to conduct a large-scale phosphoproteomic study. Some of these technologies have been successfully applied to plants with a few modifications, resulting in documentation of phosphoproteins, phosphorylation site mapping, identification of protein kinase substrates, etc. at the global level. In this review, we summarize in vitro and in vivo approaches for detection and analysis of phosphoproteins including protein kinases and we discuss the importance of phosphoproteomics in understanding plant biology. These approaches along with bioinformatics will help plant researchers to design and apply suitable phosphoproteomic strategies in helping to find answers to their biological questions.

Chromatography↗

PubMed2005

Identification of VCP/p97, carboxyl terminus of Hsp70-interacting protein (CHIP), and amphiphysin II interaction partners using membrane-based human proteome arrays.

Proteins mediate their biological function through interactions with other proteins. Therefore, the systematic identification and characterization of protein-protein interactions have become a powerful proteomic strategy to understand protein function and comprehensive cellular regulatory networks. For the screening of valosin-containing protein, carboxyl terminus of Hsp70-interacting protein (CHIP), and amphiphysin II interaction partners, we utilized a membrane-based array technology that allows the identification of human protein-protein interactions with crude bacterial cell extracts. Many novel interaction pairs such as valosin-containing protein/autocrine motility factor receptor, CHIP/caytaxin, or amphiphysin II/DLP4 were identified and subsequently confirmed by pull-down, two-hybrid and co-immunoprecipitation experiments. In addition, assays were performed to validate the interactions functionally. CHIP e.g. was found to efficiently polyubiquitinate caytaxin in vitro, suggesting that it might influence caytaxin degradation in vivo. Using peptide arrays, we also identified the binding motifs in the proteins DLP4, XRCC4, and fructose-1,6-bisphosphatase, which are crucial for the association with the Src homology 3 domain of amphiphysin II. Together these studies indicate that our human proteome array technology permits the identification of protein-protein interactions that are functionally involved in neurodegenerative disease processes, the degradation of protein substrates, and the transport of membrane vesicles.

Adenosine Triphosphatases↗

PubMed2005

High throughput identification of potential Arabidopsis mitogen-activated protein kinases substrates.

Mitogen-activated protein kinase (MAPK) cascades are universal and highly conserved signal transduction modules in eucaryotes, including plants. These protein phosphorylation cascades link extracellular stimuli to a wide range of cellular responses. However, the underlying mechanisms are so far unknown as information about phosphorylation substrates of plant MAPKs is lacking. In this study we addressed the challenging task of identifying potential substrates for Arabidopsis thaliana mitogen-activated protein kinases MPK3 and MPK6, which are activated by many environmental stress factors. For this purpose, we developed a novel protein microarray-based proteomic method allowing high throughput study of protein phosphorylation. We generated protein microarrays including 1,690 Arabidopsis proteins, which were obtained from the expression of an almost nonredundant uniclone set derived from an inflorescence meristem cDNA expression library. Microarrays were incubated with MAPKs in the presence of radioactive ATP. Using a threshold-based quantification method to evaluate the microarray results, we were able to identify 48 potential substrates of MPK3 and 39 of MPK6. 26 of them are common for both kinases. One of the identified MPK6 substrates, 1-aminocyclopropane-1-carboxylic acid synthase-6, was just recently shown as the first plant MAPK substrate in vivo, demonstrating the potential of our method to identify substrates with physiological relevance. Furthermore we revealed transcription factors, transcription regulators, splicing factors, receptors, histones, and others as candidate substrates indicating that regulation in response to MAPK signaling is very complex and not restricted to the transcriptional level. Nearly all of the 48 potential MPK3 substrates were confirmed by other in vitro methods. As a whole, our approach makes it possible to shortlist candidate substrates of mitogen-activated protein kinases as well as those of other protein kinases for further analysis. Follow-up in vivo experiments are essential to evaluate their physiological relevance.

Arabidopsis↗

PubMed2005

Multiplex approaches in protein microarray technology.

The success of genome sequencing projects has provided the basis for systematic analysis of protein function and has led to a shift from the description of single molecules to the characterization of complex samples. Such a task would not be possible without the provision of appropriate high-throughput technologies, such as protein microarray technology. In addition, the increasing number of samples necessitates the adaptation of such technologies to a multiplex format. This review will discuss protein microarray technology in the context of multiplex analysis and highlight its current prospects and limitations.

Animals↗

PubMed2004

Protein microarray technology and ultraviolet crosslinking combined with mass spectrometry for the analysis of protein-DNA interactions.

To gain insights into complex biological processes, such as transcription and replication, the analysis of protein-DNA interactions and the determination of their sequence requirements are of central importance. In this study, we probed protein microarray technology and ultraviolet crosslinking combined with mass spectrometry (MS) for their practicability to study protein-DNA interactions. We chose as a model system the well-characterized interaction of bacterial replication initiator DnaA with its cognate binding site, the DnaA box. Interactions of DnaA domain 4 with a high-affinity DnaA box (R4) and with a low-affinity DnaA box (R3) were compared. A mutant DnaA domain 4, A440V, was included in the study. DnaA domain 4, wt, spotted onto FAST slides, revealed a strong signal only with a Cy5-labeled, double-stranded, 21-mer oligonucleotide containing DnaA box R4. No signals were obtained when applying the mutant protein. Ultraviolet crosslinking combined with nanoLC/MALDI-TOF MS located the site of interaction to a peptide spanning amino acids 433- 442 of Escherichia coli DnaA. This fragment contains six residues that were identified as being involved in DNA binding by recently published crystal structure and nuclear magnetic resonance (NMR) analysis. In the future, the technologies applied in this study will become important tools for studying protein-DNA interactions.

Amino Acid Sequence↗

PubMed2004

Identification of barley CK2alpha targets by using the protein microarray technology.

We have successfully established a novel protein microarray-based kinase assay, which we applied to identify target proteins of the barley protein kinase CK2alpha. As a source of recombinant barley proteins we cloned cDNAs specific for filial tissues of developing barley seeds into an E. coli expression vector. By using robot technology, 21,500 library clones were arrayed in microtiter plates and gridded onto high-density filters. Protein expressing clones were detected using an anti-RGS-His6 antibody and rearrayed into a sublibrary of 4100 clones. All of these clones were sequenced from the 5'-end and the sequences were analysed by homology searches against protein databases. Based on these results we selected 768 clones expressing different barley proteins for protein purification. The purified proteins were robotically arrayed onto FAST slides. The generated protein microarrays were incubated with an expression library-derived barley CK2alpha in the presence of [gamma-33P]ATP, and signals were detected by X-ray film or phosphor imager. We were able to demonstrate the power of the protein microarray technology by identification of 21 potential targets out of 768 proteins including such well-known substrates of CK2alpha as high mobility group proteins and calreticulin.

Casein Kinase II↗

PubMed2002

Large-scale plant proteomics.

Large-scale and high throughput approaches increasingly play an essential role in the study of biological systems, which are per se highly complex. Therefore, they need to be examined by these extensive methods to receive information about the large genomic and proteomic networks. In plant biology, this purpose has a strong support through the accessability of the complete genome sequence of the model plant Arabidopsis thaliana. This brief review intends to focus on the basics and the state-of-the-art of these high-throughput technologies and their application to plant proteomics. It describes protein microarrays, the use of antibodies, 2-DE and MS methods and the yeast two hybrid system, which are emerging as the major technologies for plant proteomics.

Arabidopsis↗