The trypsin protease cleaves proteins on the carboxyterminus of Arginine (Arg) and Lysine (Lys). This cleavage reaction leaves a positive charge on the C-terminus of the resulting peptide, which enhances mass spectrometry analysis (1,2). Because of this advantage, trypsin has become the most commonly used protease for mass spectrometry analysis. Other proteases which cleave diffrently from trypsin, yielding complementary data are also used in mass spec analysis: these include Asp-N and Glu-C , which cleave acidic residues, and chymotrypsin which cleaves at aromatic residues. The broad spectrum protease, proteinase K is also used for some proteomic analyses. In a recent study, Dau and colleagues investigated whether sequential digestion with trypsin followed by the complementary proteases could improve protein digests for mass spectrometry analysis.Continue reading “How Can You Improve Protein Digests for Mass Spectrometry Analysis?”
Cell-free gene expression systems are a staple tool for the researcher seeking to understand the regulation of transcription and translation. Many factors can affect the efficiency of cell-free gene expression including vector sequence, reaction components and the template DNA concentration. One factor that has not been extensively studied is how DNA template length influences gene expression.Continue reading “How Does DNA Template Length Influence Gene Expression in Cell Free Systems?”
A tiny worm called Onchocerca lupi can make life uncomfortable for both humans and their best friends. This thread-like nematode is found in the eyes or under the skin of infected animals. Historically, diagnosis required skin biopsy or surgical removal of ocular tissue, but a recent study demonstrates a new non-invasive diagnostic tool for infection by Onchocerca lupi in dogs.Continue reading “Making Life Better for Man’s Best Friend: Onchocerca lupi Biomarker Characterization by Mass Spec”
Mass spectrometry depends on the successful digestion of proteins using proteases. Many commercially available proteomic-grade trypsins contain natural contaminants that produce non-specific cleavages. Trypsin Platinum, a new protease from Promega provides maximum specificity, giving you cleaner and more conclusive data from mass spec.Continue reading “The Path is Clear: Trypsin Platinum is Here!”
A new study in Nature Scientific Reports describes a method for detecting Cholangiocarcinoma biomarkers in extracellular vesicles.Continue reading “A New Method to Detect Cholangiocarcinoma Biomarkers”
A new article in Nature Scientific Reports answers open questions about TOPBP1, a protein involved in repairing DNA double-strand breaks (DSBs). The study used cell-free protein expression and a unique DSB system to identify domains that were important for activation of a protein kinase.Continue reading “Characterizing DNA Repair Proteins with Cell-Free Protein Expression”
The SARS-CoV-2 nucleocapsid protein accounts for the largest proportion of viral structural proteins and is the most abundant protein in infected cells. Nucleocapsid proteins have the job of “packaging” the viral nucleic acid (in this case, RNA). Viral nucleocapsid proteins can also enter the host nucleus and interact with a variety of host proteins to interfere with critical processes of the host cell, including protein degradation. Here we review a study that used an in vitro protein degradation assay to investigate the interaction of the SARS-CoV-2 nucleocapsid protein and the proteasome activator PA28γ.
In SARS-CoV-2 infections, the nucleocapsid protein is critical for infection, replication and packaging. The SARS-CoV-2 nucleocapsid protein is not only localized in the cytosol of the host cell but also is translocated into the nucleus. There, it interacts with various cellular proteins that modulate cellular functions, such as the degradation of unneeded or damaged proteins by proteolysis. Researchers have proposed that the protein degradation system plays an important part in coronavirus infection (1).Continue reading “SARS-CoV-2 Nucleocapsid Protein and PA28γ: A Role in Pathogenesis?”
In older people, low muscle mass is strongly associated with reduced functional capacity and an increased risk of disability. Myostatin is a negative regulator of muscle growth and has become an important target for pharmaceutical companies designing therapeutics to address age-associated muscle loss.
Anti-myostatin drugs increase muscle size and strength in preclinical studies. Fortetropin is a proteo-lipid complex made from fertilized egg yolk and shows anti-myostatin activity. When Fortetropin is provided as a supplement, lowered circulating myostatin levels are observed both in rodents and in young men. Fortetropin in combination with resistance exercise also lowers myostatin and increased lean body mass.Continue reading “More muscle from eggs? Proteo-lipid complex may help prevent age-associated loss of muscle-mass”
Glycosylation is the process by which a carbohydrate is covalently attached totarget macromolecules, typically proteins. This modification serves various functions including guiding protein folding (1,2), promoting protein stability (2), and participating signaling functions (3).
SARS-CoV-2 utilizes an extensively glycosylated spike (S) protein that protrudes from the viral surface to bind to angiotensin-converting enzyme 2 (ACE2) to mediate host-cell entry. Vaccine development has been focused on this protein, which is the focus of the humoral immune response. Understanding the glycan structure of the SARS-CoV-2 virus spike (S) protein will be critical in the development of glycoprotine-based vaccine candidates.Continue reading “Understanding the Structure of SARS-CoV-2 Spike Protein”
William G. Kaelin Jr., Sir Peter J. Ratcliffe and Gregg L. Semenza were awarded the 2019 Nobel Prize in Physiology or Medicine for their discoveries of how cells sense and adapt to oxygen availability.
Kaelin and Ratcliffe’s labs focused their efforts on the transcription factor HIF (hypoxia-inducible factor). This transcription factor is critical in the cellular adaptation of to changes in oxygen availability.
When oxygen levels are elevated cells contain very little HIF. Ubiquitin is added to the HIF protein via the VHL complex and it is degraded in the proteasome. When oxygen levels are low (hypoxia) the amount of HIF increases.
In 2001 both groups published articles characterizing the interaction between VHL and HIF, and these articles were referenced by the Nobel Prize Organization in their press release about this year’s award. (1,2). Both studies demonstrated that under the normal oxygen conditions hydroxylation of proline residue P564 enabled VHL to recognize and bind to HIF.
The use of cell free expression (i.e., TNT Coupled Transcription/Translation System) by both labs was key in the characterization of the VHL:HIF interaction The labs utilized HIF and VHL 35-S labeled proteins generated via the TNT system under both normal or in a hypoxic work station to:
- Determine the affect of ferrous chloride and cobaltous chloride on the interaction
- Map the specific region of HIF required for the interaction to occur (556-574)
- Determine the effect of HIF point mutations on the interaction
- Use synthetic peptides to block the interaction
- Conclude that a factor in mammalian cells was necessary for the interaction to occur.
- Ivan, M et al. (2001) HIF Targeted for VHL-Mediated Destruction by Proline Hydroxylation: Implications for O2 Sensing. Science 292: 464–67.
- Jaakkola, P. et al. (2001) Targeting of HIF-α to the von Hippel-Lindau Ubiquitylation of Complex by O2– Regulated Prolyl Hydroxylation. Science 202, 468–72 .