Project description:A comprehensive analysis of the phosphoproteome is essential for understanding molecular mechanisms of human diseases. However, current tools to enrich phosphotyrosine are limited in their applicability and scope. Here, we engineered new superbinder SH2 domains that enrich diverse sets of phosphotyrosine peptides. We used phage display to select a Fes SH2 domain variant with high affinity for phosphotyrosine (superFes-SH2, sFes1) and solved the structure of sFes1 bound to a phosphopeptide. We performed systematic structure-function analyses of the superbinding mechanisms of sFes1 and superSrc-SH2 (sSrc1), another SH2-superbinder. We grafted the superbinder motifs from sFes1 and sSrc1 into 17 additional SH2 domains and confirmed increased binding affinity for specific phosphopeptides. Using mass spectrometry, we demonstrated that SH2 superbinders have distinct specificity profiles and superior capabilities to enrich phosphotyrosine peptides. Finally, combinations of SH2 superbinders as affinity purification tools showed that unique subsets of phosphopeptides can be enriched with unparalleled depth and coverage.
Project description:Mirror-image proteins, composed of D-amino acids, are an attractive therapeutic modality, as they exhibit high metabolic stability and lack immunogenicity. Development of mirror-image binding proteins is achieved through chemical synthesis of D-target proteins, phage display library selection of L-binders and chemical synthesis of (mirror-image) D binders that consequently bind the physiological L-targets. Monobodies are well-established synthetic (L )binding proteins and their small size (~90 residues) and lack of endogenous cysteine residues make them particularly accessible to chemical synthesis. Here, we developed monobodies with nanomolar binding affinities against the D-SH2 domain of the leukemic tyrosine kinase BCR::ABL1. Two crystal structures of heterochiral monobody-SH2 complexes revealed targeting of the pY binding pocket by an unconventional binding mode. We then prepared potent D-monobodies by either ligating two chemically synthesized D-peptides or by self-assembly without ligation. Their proper folding and stability were determined and high affinity binding to the L-target was shown. D-monobodies were protease-resistant, showed long-term plasma stability, inhibited BCR::ABL1 kinase activity and bound BCR::ABL1 in cells and (to some extent in) cell lysates with high selectivity. Hence, we demonstrate that functional D monobodies can be developed readily. Our work represents an important step towards the possible future therapeutic use of D-monobodies when combined with emerging methods to enable cytoplasmic delivery of monobodies.
Project description:Single cell multi-omic readouts of both the cellular transcriptome and proteome have significantly enhanced our ability to comprehensively characterize cellular states. Most approaches in this area rely on oligonucleotide barcode-conjugated antibodies that target cell surface epitopes of interest, enabling their concomitant detection with the transcriptome. However, a similar high-throughput measurement of other cellular modalities such as the epigenome in concert with protein levels have not been described. Moreover, detection of epitopes is limited to antigens for which a specific antibody is available. Here, we introduce PHAGE-ATAC, an approach that enables the scalable and simultaneous detection of protein levels and chromatin accessibility data in single cells using the assay of transposase-accessible chromatin with sequencing (ATAC-seq). Quantitative detection of proteins by PHAGE-ATAC is accomplished through the use of engineerable nanobody-displaying phages that are genetically barcoded within the nanobody-encoding phagemids. We demonstrate the utility of PHAGE-ATAC for multimodal single cell genomic analysis in both cell lines and primary human cells. Analogous to phage display approaches, we further establish a synthetic high-complexity library of nanobody-displaying phages and demonstrate its utility to select novel antigen-specific nanobodies for PHAGE-ATAC.
Project description:Single cell multi-omic readouts of both the cellular transcriptome and proteome have significantly enhanced our ability to comprehensively characterize cellular states. Most approaches in this area rely on oligonucleotide barcode-conjugated antibodies that target cell surface epitopes of interest, enabling their concomitant detection with the transcriptome. However, a similar high-throughput measurement of other cellular modalities such as the epigenome in concert with protein levels have not been described. Moreover, detection of epitopes is limited to antigens for which a specific antibody is available. Here, we introduce PHAGE-ATAC, an approach that enables the scalable and simultaneous detection of protein levels and chromatin accessibility data in single cells using the assay of transposase-accessible chromatin with sequencing (ATAC-seq). Quantitative detection of proteins by PHAGE-ATAC is accomplished through the use of engineerable nanobody-displaying phages that are genetically barcoded within the nanobody-encoding phagemids. We demonstrate the utility of PHAGE-ATAC for multimodal single cell genomic analysis in both cell lines and primary human cells. Analogous to phage display approaches, we further establish a synthetic high-complexity library of nanobody-displaying phages and demonstrate its utility to select novel antigen-specific nanobodies for PHAGE-ATAC.
Project description:Single cell multi-omic readouts of both the cellular transcriptome and proteome have significantly enhanced our ability to comprehensively characterize cellular states. Most approaches in this area rely on oligonucleotide barcode-conjugated antibodies that target cell surface epitopes of interest, enabling their concomitant detection with the transcriptome. However, a similar high-throughput measurement of other cellular modalities such as the epigenome in concert with protein levels have not been described. Moreover, detection of epitopes is limited to antigens for which a specific antibody is available. Here, we introduce PHAGE-ATAC, an approach that enables the scalable and simultaneous detection of protein levels and chromatin accessibility data in single cells using the assay of transposase-accessible chromatin with sequencing (ATAC-seq). Quantitative detection of proteins by PHAGE-ATAC is accomplished through the use of engineerable nanobody-displaying phages that are genetically barcoded within the nanobody-encoding phagemids. We demonstrate the utility of PHAGE-ATAC for multimodal single cell genomic analysis in both cell lines and primary human cells. Analogous to phage display approaches, we further establish a synthetic high-complexity library of nanobody-displaying phages and demonstrate its utility to select novel antigen-specific nanobodies for PHAGE-ATAC.
Project description:The protein modules known as SH2 (Src-homology-2) domains are key players in the signal transduction of animals. Two questions arise: Do such modules exist in plants, and when did SH2 domains evolve? Here I show that the Arabidopsis genome contains three strong candidates for plant SH2 proteins (referred to as PASTA1, 2 and 3 : GI:25513455, At1g78540, At1g17040 respectively) with homology to the SH2 domains and the adjacent linker region of STAT proteins (Signal Transducer and Activator of Transcription). The three characteristics features of a STAT protein sequence1, namely, (i) the SH2 domain with a conserved arginine residue crucial for binding to a phospho-tyrosine residue (ii) a tyrosine residue outside the C-terminus of the SH2-domain for phosphorylation during signalling and (iii) a DNA-binding domain, are conserved in the PASTA3 protein. However, PASTA 1 and 2 proteins lack a tyrosine in a similar position. PASTA proteins are not homologous to STAT proteins outside the SH2 and linker regions. The three PASTA proteins are 70 to 80 % identical to one another. Gene expression studies with PASTA2 reveal that it is expressed in roots, stem, leaves, flowers and green siliques. Preliminary indications are that plants homozygous for PASTA2 do not have any obvious phenotype, most likely due to redundancies. This microarray experiment is an attempt to compare the gene expression of a mutant plant homozygous for PASTA2 with that of the wild type plant. This might give clues about the possible function of PASTA2 in Arabidopsis.
Project description:We present a target-unbiased approach for antibody discovery that relies on generating mAbs against native target cell surfaces via phage display. This method combines a previously reported method for improved whole-cell phage display selections with next-generation sequencing analysis to efficiently identify mAbs with the desired target cell reactivity. This approach enabled the identification of three multiple myeloma cell surface antigens, and cognate monoclonal antibody probes.
Project description:Gene expression analysis by high-throughtput RNA-sequencing from roots of waterlogged jatropha (Jatropha curcas). Six leaf stage seedlings (~30 d.o.) were subjected to 24 h of soil waterlogging.