Project description:Identification of targets of the protein disulfide reductase thioredoxin using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) and thiol specific differential labeling with isotope-coded affinity tags (ICAT). Reduction of specific target disulfides is quantified by measuring ratios of cysteine residues labeled with the heavy (13C) and light (12C) ICAT reagents in peptides derived from tryptic digests of Trx-treated and non-treated samples. Keywords: protein, LC-MS/MS, ICAT
Project description:Trypsin is the protease of choice in bottom-up proteomics. However, its application can be limited by the amino acid composition of target proteins and the pH of digestion solution. In this study we characterized ProAlanase, a protease from the fungus Aspergillus niger that cleaves primarily on the C-terminal side of proline and alanine residues. ProAlanase achieves high proteolytic activity and specificity when digestions are carried out at acidic pH (1.5) for relatively short (2 hr) time periods. To elucidate the potential of ProAlanase in proteomic applications, we conducted a series of investigations comprising digestion of proline-rich proteins, PTM analysis, de novo protein sequencing and disulfide bond mapping. The results demonstrated that digestion with ProAlanase improves protein sequence coverage and phosphosite localization for the proline-rich protein Notch3 intracellular domain and improves non-collagenous bone protein identification. Notably, cleavage also occurs at the C-terminus of hydroxyproline, facilitating efficient digestion of bone collagen. Finally, we demonstrate that ProAlanase is efficient in disulfide bond mapping, showing high coverage of disulfide-containing regions in monoclonal antibodies, as well as achieving nearly complete database-independent sequence reconstruction of endogenous protein by de novo sequencing.
Project description:The Thr654Cys and Thr661Cys mutations were used to introduce a disulfide bridge into the interacting LNK domains of human A2M. In this study, formation of the disulfide was investigated by mass spectrometry.
Project description:Understanding the conformational sampling of translation-arrested ribosome nascent chain complexes is key to understand co-translational folding. Up to now, coupling of cysteine oxidation, disulfide bond formation and structure formation in nascent chains has remained elusive. Here, we investigate the eye-lens protein γB-crystallin in the ribosomal exit tunnel. Using mass spectrometry, theoretical simulations, dynamic nuclear polarization-enhanced solid-state nuclear magnetic resonance and cryo-electron microscopy, we show that thiol groups of cysteine residues undergo S-glutathionylation and S-nitrosylation and form non-native disulfide bonds. Thus, covalent modification chemistry occurs already prior to nascent chain release as the ribosome exit tunnel provides sufficient space even for disulfide bond formation which can guide protein folding.
Project description:Trypsin is the protease of choice in bottom-up proteomics. However, its application can be limited by the amino acid composition of target proteins and the pH of digestion solution. In this study we characterized ProAlanase, a protease from the fungus Aspergillus niger that cleaves primarily on the C-terminal side of proline and alanine residues. ProAlanase achieves high proteolytic activity and specificity when digestions are carried out at acidic pH (1.5) for relatively short (2 hr) time periods. To elucidate the potential of ProAlanase in proteomic applications, we conducted a series of investigations comprising digestion of proline-rich proteins, PTM analysis, de novo protein sequencing and disulfide bond mapping. The results demonstrated that digestion with ProAlanase improves protein sequence coverage and phosphosite localization for the proline-rich protein Notch3 intracellular domain and improves non-collagenous bone protein identification. Notably, cleavage also occurs at the C-terminus of hydroxyproline, facilitating efficient digestion of bone collagen. Finally, we demonstrate that ProAlanase is efficient in disulfide bond mapping, showing high coverage of disulfide-containing regions in monoclonal antibodies, as well as achieving nearly complete database-independent sequence reconstruction of endogenous protein by de novo sequencing.
Project description:In this study, AC2P20 was prioritized for continued study to test the hypothesis that it was targeting Mtb pathways associated with pH-driven adaptation. RNAseq transcriptional profiling studies showed AC2P20 modulates expression of genes associated with redox-homeostasis. Gene enrichment analysis revealed that the AC2P20 transcriptional profile had significant overlap with a previously characterized pH-selective inhibitor, AC2P36. Like AC2P36, we show that AC2P20 kills Mtb by selectively depleting free thiols at acidic pH. Mass spectrometry studies show the formation of a disulfide bond between AC2P20 and reduced glutathione, supporting a mechanism where AC2P20 is able to deplete intracellular thiols and dysregulate redox homeostasis.
Project description:The protein secretory pathway must maintain homoeostasis while producing a wide assortment of proteins in different conditions. It is also used extensively to produce many useful proteins in biotechnology. As such, secretory pathway dysfunction can be highly detrimental to the cell, resulting in the molecular basis for many human diseases, and can drastically inhibit product titers in biochemical production. Because the secretory pathway is a highly-integrated, multi-organelle system, dysfunction can happen at many levels and dissecting the root cause can be challenging. To better understand some of these dysfunctions, we measured multiple systems-level states of the cell (physiology, transcriptome, metabolism) while secreting a small protein (insulin precursor) or a large protein (α-amylase). This was carried out in the presence and absence of HAC1, a key transcription factor in maintaining secretory homeostasis. Clear trends in cellular stress were apparent across multiple data resulting from our perturbations. In particular, processes involving (1) degradation of protein / recycling amino acids, (2) overall transcription/translation repression, and (3) oxidative stress. Apparent runaway oxidative radical production was explained by a thermodynamic model that we put forward for disulfide formation in the endoplasmic reticulum. This model predicts that balancing the relative rates of protein folding and disulfide bond formation are key to easing oxidative stress. These predictions have direct implications in how to engineer a broad range of recombinant proteins for secretion and provide potential hypotheses for the root causes of several secretory-associated diseases.
Project description:The protein secretory pathway must maintain homoeostasis while producing a wide assortment of proteins in different conditions. It is also used extensively to produce many useful proteins in biotechnology. As such, secretory pathway dysfunction can be highly detrimental to the cell, resulting in the molecular basis for many human diseases, and can drastically inhibit product titers in biochemical production. Because the secretory pathway is a highly-integrated, multi-organelle system, dysfunction can happen at many levels and dissecting the root cause can be challenging. To better understand some of these dysfunctions, we measured multiple systems-level states of the cell (physiology, transcriptome, metabolism) while secreting a small protein (insulin precursor) or a large protein (?-amylase). This was carried out in the presence and absence of HAC1, a key transcription factor in maintaining secretory homeostasis. Clear trends in cellular stress were apparent across multiple data resulting from our perturbations. In particular, processes involving (1) degradation of protein / recycling amino acids, (2) overall transcription/translation repression, and (3) oxidative stress. Apparent runaway oxidative radical production was explained by a thermodynamic model that we put forward for disulfide formation in the endoplasmic reticulum. This model predicts that balancing the relative rates of protein folding and disulfide bond formation are key to easing oxidative stress. These predictions have direct implications in how to engineer a broad range of recombinant proteins for secretion and provide potential hypotheses for the root causes of several secretory-associated diseases. Yeast strains were constructed that produce and secrete (a) IP or (b) ?-amylase and were compared to yeast strains containing (c) an empty vector in both wild-type and HAC1 deletion backgrounds. These strains are named WN (WT with empty vector), WI (WT secreting IP), WA (WT secreting ?-amylase), dN (?hac1 with empty vector), dI (?hac1 secreting IP), and dA (?hac1 secreting ?-amylase). Strains were characterized in batch fermentation and samples were taken in mid-exponential phase. Triplicate fermentations were carried out for each strain.
Project description:The αIIbβ3 integrin receptor coordinates platelet adhesion, activation and mechanosensing in thrombosis and haemostasis. Using differential cysteine alkylation and mass spectrometry, we have identified a disulfide bond in the αIIb subunit linking cysteines 490 and 545 that is missing in about one in three integrin molecules on the resting and activated human platelet surface. This alternate covalent form of αIIbβ3 is pre-determined as it is also produced by human megakaryoblasts and bovine hamster kidney cells transfected with recombinant human integrin. From co-immunoprecipitation experiments, the alternate form selectively partitions into focal adhesions on the activated platelet surface. Its function was evaluated in bovine hamster kidney cells expressing a mutant integrin with an ablated C490-C545 disulfide bond. The disulfide mutant integrin has extended residency time in focal adhesions due to reduced rate of clathrin-mediated integrin internalisation and recycling that is associated with enhanced affinity of the αIIb subunit for clathrin adaptor protein-2. The alternate covalent form also has different conformational dynamics measured by monoclonal antibody binding and molecular dynamic simulations, which is reflected in reduced fibrinogen binding and outside-in signalling. These findings indicate that the αIIbβ3 integrin receptor is produced in different covalent forms that have different functions. The C490, C545 cysteine pair is conserved across all 18 integrin α subunits and the disulfide bond in αV in a cancer cell line is similarly missing, suggesting that this alternate integrin form and function is also conserved.
Project description:Trypsin is the protease of choice in bottom-up proteomics. However, its application can be limited by the amino acid composition of target proteins and the pH of the digestion solution. In this study we characterize ProAlanase, a protease from the fungus Aspergillus niger that cleaves primarily on the C-terminal side of proline and alanine residues. ProAlanase achieves high proteolytic activity and specificity when digestion is carried out at acidic pH (1.5) for relatively short (2 h) time periods. To elucidate the potential of ProAlanase in proteomics applications, we conducted a series of investigations comprising comparative multi-enzymatic profiling of a human cell line proteome, histone PTM analysis, ancient bone protein identification, phosphosite mapping and de novo sequencing of a proline-rich protein and disulfide bond mapping in monoclonal antibody. The results demonstrate that ProAlanase is highly suitable for proteomics analysis of the arginine- and lysine-rich histones, enabling high sequence coverage of multiple histone family members. It also facilitates an efficient digestion of bone collagen thanks to the cleavage at the C-terminus of hydroxyproline which is highly prevalent in collagen. This allows to identify complementary proteins in ProAlanase- and trypsin-digested ancient bone samples, as well as to increase sequence coverage of non-collagenous proteins. Moreover, digestion with ProAlanase improves protein sequence coverage and phosphosite localization for the proline-rich protein Notch3 intracellular domain (N3ICD). Furthermore, we achieve a nearly complete coverage of N3ICD protein by de novo sequencing using the combination of ProAlanase and tryptic peptides. Finally, we demonstrate that ProAlanase is efficient in disulfide bond mapping, showing high coverage of disulfide-containing regions in a non-reduced monoclonal antibody.