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The notion that protein function is allosterically regulated by structural or dynamic changes in proteins has been extensively investigated in several protein domains in isolation. In particular, PDZ domains have represented a paradigm for these studies, despite providing conflicting results. Furthermore, it is still unknown how the association between protein domains in supramodules, consitituting so-called supertertiary structures, affects allosteric networks. Here, we experimentally mapped the allosteric network in a PDZ:ligand complex, both in isolation and in the context of a supramodular structure, and show that allosteric networks in a PDZ domain are highly dependent on the supertertiary structure in which they are present. This striking sensitivity of allosteric networks to the presence of adjacent protein domains is likely a common property of supertertiary structures in proteins. Our findings have general implications for prediction of allosteric networks from primary and tertiary structures and for quantitative descriptions of allostery.

Viral proteins make extensive use of short peptide interaction motifs to hijack cellular host factors. However, most current large-scale methods do not identify this important class of protein-protein interactions. Uncovering peptide mediated interactions provides both a molecular understanding of viral interactions with their host and the foundation for developing novel antiviral reagents. Here we describe a viral peptide discovery approach covering 23 coronavirus strains that provides high resolution information on direct virus-host interactions. We identify 269 peptide-based interactions for 18 coronaviruses including a specific interaction between the human G3BP1/2 proteins and an ΦxFG peptide motif in the SARS-CoV-2 nucleocapsid (N) protein. This interaction supports viral replication and through its ΦxFG motif N rewires the G3BP1/2 interactome to disrupt stress granules. A peptide-based inhibitor disrupting the G3BP1/2-N interaction dampened SARS-CoV-2 infection showing that our results can be directly translated into novel specific antiviral reagents. Many interactions between viral and host proteins are mediated by short peptide motifs. Here, using a phage-based viral peptide library, the authors identify 269 peptide-based interactions for 18 coronaviruses, including an interaction between SARS-CoV-2 N and G3BP1/2 that affects stress granules.

Specific protein–protein interactions are central to all processes that underlie cell physiology. Numerous studies have together identified hundreds of thousands of human protein–protein interactions. However, many interactions remain to be discovered, and low affinity, conditional, and cell type‐specific interactions are likely to be disproportionately underrepresented. Here, we describe an optimized proteomic peptide‐phage display library that tiles all disordered regions of the human proteome and allows the screening of ~ 1,000,000 overlapping peptides in a single binding assay. We define guidelines for processing, filtering, and ranking the results and provide PepTools, a toolkit to annotate the identified hits. We uncovered >2,000 interaction pairs for 35 known short linear motif (SLiM)‐binding domains and confirmed the quality of the produced data by complementary biophysical or cell‐based assays. Finally, we show how the amino acid resolution‐binding site information can be used to pinpoint functionally important disease mutations and phosphorylation events in intrinsically disordered regions of the proteome. The optimized human disorderome library paired with PepTools represents a powerful pipeline for unbiased proteome‐wide discovery of SLiM‐based interactions. Synopsis An optimized phage peptidome that tiles the disordered regions of the human proteome is presented, allowing the field of motif‐based interactions to transition into high‐throughput. Guidelines and tools for data analysis are provided. An optimized second generation human disorderome (HD2) phage library tiles all disordered regions from the human proteome. Different peptide display parameters are tested, including display on the major or minor coat proteins of the M13 phage, and splitting the library design based sub‐cellular localization of the peptide containing proteins. PepTools is a dedicated toolkit to annotate peptides and to identify consensus motifs. > 2,000 motif‐based interactions are presented, together with information on potential disease mutations or phosphorylation sites that might affect the interactions. Graphical Abstract An optimized phage peptidome that tiles the disordered regions of the human proteome is presented, allowing the field of motif‐based interactions to transition into high‐throughput. Guidelines and tools for data analysis are provided.

Whole genome and exome sequencing are reporting on hundreds of thousands of missense mutations. Taking a pan-disease approach, we explored how mutations in intrinsically disordered regions (IDRs) break or generate protein interactions mediated by short linear motifs. We created a peptide-phage display library tiling ~57,000 peptides from the IDRs of the human proteome overlapping 12,301 single nucleotide variants associated with diverse phenotypes including cancer, metabolic diseases and neurological diseases. By screening 80 human proteins, we identified 366 mutation-modulated interactions, with half of the mutations diminishing binding, and half enhancing binding or creating novel interaction interfaces. The effects of the mutations were confirmed by affinity measurements. In cellular assays, the effects of motif-disruptive mutations were validated, including loss of a nuclear localisation signal in the cell division control protein CDC45 by a mutation associated with Meier-Gorlin syndrome. The study provides insights into how disease-associated mutations may perturb and rewire the motif-based interactome. Synopsis Hundreds of mutations in the intrinsically disordered regions of the human proteome that break, diminish, enhance or create motif-based interactions are uncovered by mutational proteomic peptide-phage display. A novel peptide-phage display library that combines disease-associated amino acid changing mutations with the intrinsically disordered regions of the human proteome is described. 275 mutations associated with various diseases are reported to affect 279 motif-based protein-protein interactions. About 50% of the mutations enhance or create binding motifs, and the rest disrupt or diminish interactions. The study provides novel insights into how disease-associated mutations perturb and rewire the motif-based interactome. Hundreds of mutations in the intrinsically disordered regions of the human proteome that break, diminish, enhance or create motif-based interactions are uncovered by mutational proteomic peptide-phage display.

Phosphorylation is a ubiquitous post‐translation modification that regulates protein function by promoting, inhibiting or modulating protein–protein interactions. Hundreds of thousands of phosphosites have been identified but the vast majority have not been functionally characterised and it remains a challenge to decipher phosphorylation events modulating interactions. We generated a phosphomimetic proteomic peptide‐phage display library to screen for phosphosites that modulate short linear motif‐based interactions. The peptidome covers ~13,500 phospho‐serine/threonine sites found in the intrinsically disordered regions of the human proteome. Each phosphosite is represented as wild‐type and phosphomimetic variant. We screened 71 protein domains to identify 248 phosphosites that modulate motif‐mediated interactions. Affinity measurements confirmed the phospho‐modulation of 14 out of 18 tested interactions. We performed a detailed follow‐up on a phospho‐dependent interaction between clathrin and the mitotic spindle protein hepatoma‐upregulated protein (HURP), demonstrating the essentiality of the phospho‐dependency to the mitotic function of HURP. Structural characterisation of the clathrin‐HURP complex elucidated the molecular basis for the phospho‐dependency. Our work showcases the power of phosphomimetic ProP‐PD to discover novel phospho‐modulated interactions required for cellular function. Synopsis A new phosphomimetic proteomic peptide phage library is used to screen for phospho‐modulated interactions between short linear motifs and protein domains. Follow‐up analyses show that S839 phosphorylation of HURP is required for interaction with clathrin and mitotic function. A novel phosphomimetic ProP‐PD library is generated, displaying intrinsically disordered regions of the proteome with functionally prioritised phosphosites. Phosphomimetic ProP‐PD selections provide binding preferences for wild‐type, phosphomimetic and phosphorylated peptides at large‐scale. S839 HURP phosphorylation is required for clathrin binding and its role in mitosis. SLiM‐based interactions from ProP‐PD selections are available in a web‐based resource ( http://slim.icr.ac.uk/proppd/ ). Graphical Abstract A new phosphomimetic proteomic peptide phage library is used to screen for phospho‐modulated interactions between short linear motifs and protein domains. Follow‐up analyses show that S839 phosphorylation of HURP is required for interaction with clathrin and mitotic function.

Many regulatory protein-protein interactions depend on Short Linear Motifs (SLiMs). In the cell cycle, cyclin-CDKs recognize SLiMs to control substrate recruitment and phosphorylation timing. Here, we measure the relative binding strength of ~100,000 peptides to 11 human cyclins from five families (D, E, A, B, and F). Using a quantitative intracellular binding assay and large-scale tiled peptide screening, we identify multiple non-canonical binders unveiling a broader repertoire of cyclin docking motif types. Cryo-electron microscopy and saturation mutagenesis studies reveal distinct binding modes and sequence features governing motif recognition, binding strength, and cyclin preference. Docking motifs vary from highly selective to pan-cyclin, thereby fine-tuning the timing of CDK phosphorylation during cell cycle. Overall, these findings provide insights into the rules encoding specificity and affinity of SLiM-mediated interactions and offer a framework for understanding motif-driven protein networks across the proteome. Many protein–protein interactions depend on Short Linear Motifs (SLiMs). In this study, the authors use large-scale binding assays, deep mutational scanning, and structural analysis to map SLiMs recognised by human cyclins and uncover the rules that determine their specificity and affinity.

Cyclin-CDKs are master regulators of cell division. In addition to directly activating the CDK, the cyclin subunit regulates CDK specificity by binding short peptide \"docking\" motifs in CDK substrates. Here, we measure the relative binding strength of ~100,000 peptides to 11 human cyclins from five cyclin families (D, E, A, B and F). Using a quantitative intracellular binding assay and large-scale tiled peptide screening, we identified a range of non-canonical binders that unveil a broader than anticipated repertoire of cyclin docking motif types. Structural and saturation mutagenesis studies revealed distinct binding modes and sequence features that govern motif recognition, binding strength, and cyclin preference. Docking motifs vary from highly selective to pan-cyclin, thereby fine-tuning the timing of CDK phosphorylation during cell cycle progression. Overall, these findings provide an unprecedented depth of understanding about the rules encoding specificity and affinity within a group of related but distinct protein domains.

Abstract The spike protein of the SARS-CoV-2 interacts with angiotensin converting enzyme 2 (ACE2) and enters the host cell by receptor-mediated endocytosis. Concomitantly, evidence is pointing to the involvement of additional host cell receptors, such as integrins. The cytoplasmic tails of ACE2 and integrin β3 contain a plethora of predicted binding motifs. Here, we confirm the functionality of some of these motifs through affinity measurements. The class I PDZ binding motif in the ACE2 cytoplasmic tail binds the first PDZ domain of the scaffold protein NHERF3. The clathrin-adaptor subunit AP2 μ2 interacts with an endocytic motif in the ACE2 with low affinity and the interaction is abolished by phosphorylation of Tyr781. Furthermore, the C-terminal region of integrin b3 contains a LC3-interacting region, and its interaction with ATG8 domains is enhanced by phosphorylation. Together, our data provides possible molecular links between host cell receptors and endocytosis and autophagy. One sentence summary Affinity measurements confirmed binding of short linear motifs in the cytoplasmic tails of ACE2 and integrin β3, thereby linking the receptors to endocytosis and autophagy. Competing Interest Statement The authors have declared no competing interest.

Whole genome and exome sequencing are reporting on hundreds of thousands of missense mutations. Taking a pan-disease approach, we explored how mutations in the intrinsically disordered regions (IDRs) break or generate protein interactions mediated by short linear motifs. We created a peptide-phage display library tiling ∼57,000 peptides from the IDRs of the human proteome overlapping 12,301 single nucleotide variant associated with diverse phenotypes including cancer, metabolic diseases and neurological diseases. By screening 80 human proteins, we identified 366 mutation-modulated interactions, with half of the mutations diminishing binding, and half enhancing binding or creating novel interaction interfaces. The effects of the mutations were confirmed by affinity measurements. In cellular assays, the effects of motif-disruptive mutations were validated, including loss of a nuclear localisation signal in the cell division control protein CDC45 by a mutation associated with Meier-Gorlin syndrome. The study provides insights into how disease-associated mutations may perturb and rewire the motif-based interactome.

The notion that protein function is allosterically regulated by structural or dynamic changes in proteins has been extensively investigated in several protein domains in isolation. In particular, PDZ domains have represented a paradigm for these studies, despite providing conflicting results. Furthermore, it is still unknown how the association between protein domains in supramodules, consitituting so-called supertertiary structure, affects allosteric networks. Here, we experimentally mapped the allosteric network in a PDZ:ligand complex, both in isolation and in the context of a supramodular structure, and show that allosteric networks in a PDZ domain are highly dependent on the supertertiary structure in which they are present. This striking sensitivity of allosteric networks to presence of adjacent protein domains is likely a common property of supertertiary structures in proteins. Our findings have general implications for prediction of allosteric networks from primary and tertiary structure and for quantitative descriptions of allostery.