The protein phosphatses of arabidopsis thaliana: bioinformatics, biochemistry and function

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My research program focuses on a group of highly conserved enzymes (proteins) called protein phosphatases. Most cellular proteins get modified in the cell in very specific ways to allow control of their function in response to signals from outside or within the cell. The most common means of modifying a protein is the covalent attachment of a phosphate group. This is referred to as protein phosphorylation and the enzymes that add this phosphate are called protein kinases and the enzymes that remove this phosphate are protein phosphatases. My group works with the model plant Arabidopsis thaliana and by using the publicly available genome sequence data and information from other well characterized organisms (like humans and yeast) we have identified a complete set of protein phosphatases in this organism. By examining the amino acid sequence of these protein phosphatases we have been able to predict certain features for several of these enzymes and we are now doing the biochemistry and cell biology to further define the properties and role of these enzymes. My group is focusing on the type one phosphatases (PP1), which are regulated by targeting subunits that define their function. As yet, no targeting subunits are known in plants. Using affinity chromatography and mass spectrometry we have identified 20 binding proteins and propose to perform a detailed characterization for 3 of them, including the putative nucleoside kinase ZAP3. Through bioinformatic insights we have also focused our attention on a completely novel chloroplast localized phosphatase. This enzyme is being characterized and we believe it may represent an ancient or ancestral form of the type one or 2A phosphatases. By using affinity chromatography and mass spectrometry as a starting point, we have also identified a type 2A (PP2A) complex that interacts with several other cellular proteins and plays a role in controlling the trafficking of protein cargo in the cell. My research program is making the critical bridge between computer-based observations (bioinformatics) and the biochemistry, molecular and cell biology necessary to support these observations.