ProFeatMap: a highly customizable tool for 2D feature representation of protein sets.

Motivation: Studies of sets of proteins are a central point in biology. In particular, the application of omics in the last decades has generated lists of several hundreds or thousands of proteins or genes. However, these lists are often not inspected globally, possibly due to the lack of tools capable of simultaneously visualizing the feature architectures of a large number of proteins. Results: Here, we present ProFeatMap, an intuitive Python-based website. For a given set of proteins, it allows to display features such as domains, repeats, disorder or post-translational modifications and their organization along the sequences, into a highly customizable 2D map. Starting from a user-defined protein list of UniProt accession codes, ProFeatMap extracts the most important annotated features available for each protein from one of the well-established databases such as Uniprot or InterPro, allocates shapes and colors, potentially depending on quantitative or qualitative data and sorts the protein list based on homologous feature content. The resulting publication-quality map allows even large protein families to be explored, and to classify them based on shared features. It can help to gain insights, for example, feature redundancy or feature pattern, that were previously overlooked. ProFeatMap is freely available on the web at: https://profeatmap.pythonanywhere.com/. Availability and implementation: Source code is freely accessible at https://github.com/profeatmap/ProFeatMap under the GPL license. Supplementary information: Supplementary data are available at Bioinformatics Advances online.

A Computational Protocol to Analyze PDZ/PBM Affinity Data Obtained by High-Throughput Holdup Assay.

The holdup assay is an automated high-throughput comparative chromatographic retention approach that allows to measure quantitative binding intensities (BI) for a large number of domain-motif pairs and deduce equilibrium binding affinity constants. We routinely apply this approach to obtain quantitative binding specificity profiles of particular PDZ-binding motifs (PBMs) toward the full library of known human PDZ domains (the PDZome). The quality of the electropherograms extracted from the capillary electrophoresis instrument at the final step of the holdup assay may vary, influencing the accuracy and reproducibility of the measurement. By using bioinformatic tools, we can solve these issues to extract more reliable BIs by means of a better superimposition of the electropherograms. The protocol presented in this chapter describes the main principles and strategies of our curated method to process holdup data and new ways to plot and compare the BIs for the PBM-PDZ interactions. For this particular protocol, all the necessary computing commands are freely available in open Python packages.

Interactomic affinity profiling by holdup assay: Acetylation and distal residues impact the PDZome-binding specificity of PTEN phosphatase.

Protein domains often recognize short linear protein motifs composed of a core conserved consensus sequence surrounded by less critical, modulatory positions. PTEN, a lipid phosphatase involved in phosphatidylinositol 3-kinase (PI3K) pathway, contains such a short motif located at the extreme C-terminus capable to recognize PDZ domains. It has been shown that the acetylation of this motif could modulate the interaction with several PDZ domains. Here we used an accurate experimental approach combining high-throughput holdup chromatographic assay and competitive fluorescence polarization technique to measure quantitative binding affinity profiles of the PDZ domain-binding motif (PBM) of PTEN. We substantially extended the previous knowledge towards the 266 known human PDZ domains, generating the full PDZome-binding profile of the PTEN PBM. We confirmed that inclusion of N-terminal flanking residues, acetylation or mutation of a lysine at a modulatory position significantly altered the PDZome-binding profile. A numerical specificity index is also introduced as an attempt to quantify the specificity of a given PBM over the complete PDZome. Our results highlight the impact of modulatory residues and post-translational modifications on PBM interactomes and their specificity.

Dual Specificity PDZ- and 14-3-3-Binding Motifs: A Structural and Interactomics Study.

Protein-protein interaction motifs are often alterable by post-translational modifications. For example, 19% of predicted human PDZ domain-binding motifs (PBMs) have been experimentally proven to be phosphorylated, and up to 82% are theoretically phosphorylatable. Phosphorylation of PBMs may drastically rewire their interactomes, by altering their affinities for PDZ domains and 14-3-3 proteins. The effect of phosphorylation is often analyzed by performing "phosphomimetic" mutations. Here, we focused on the PBMs of HPV16-E6 viral oncoprotein and human RSK1 kinase. We measured the binding affinities of native, phosphorylated, and phosphomimetic variants of both PBMs toward the 266 human PDZ domains. We co-crystallized all the motif variants with a selected PDZ domain to characterize the structural consequence of the different modifications. Finally, we elucidated the structural basis of PBM capture by 14-3-3 proteins. This study provides novel atomic and interactomic insights into phosphorylatable dual specificity motifs and the differential effects of phosphorylation and phosphomimetic approaches.