Cysteine Proteinases
Cysteine Proteinases - Related Videos
09:14
Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry
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Cited by 8 •
2016
This protocol details the important steps required for the bioconjugation of a cysteine containing protein to a maleimide, including reagent purification, reaction conditions, bioconjugate purification and bioconjugate characterization.
03:27
Labeling of Surface-Accessible Cysteine Residues in Engineered Virus-Like Particles
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2026
Source: Natilla, A.,and Hammond, R. W. Analysis of the Solvent Accessibility of Cysteine Residues on Maize rayado fino virus Virus-like Particles Produced in Nicotiana benthamiana Plants and Cross-linking of Peptides to VLPs. J. Vis. Exp. (2013)This video demonstrates site-specific fluorescent labeling of mutant virus-like particles (VLPs) produced in Nicotiana benthamiana using a thiol-reactive dye, followed by purification and gel electrophoresis to confirm surface modification.
08:14
Analysis of the Solvent Accessibility of Cysteine Residues on Maize rayado fino virus Virus-like Particles Produced in Nicotiana benthamiana Plants and Cross-linking of Peptides to VLPs
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Cited by 3 •
2013
A method to analyze the solvent accessibility of the thiol group of cysteine residues of Maize rayado fino virus (MRFV)-virus-like particles (VLPs) followed by a peptide cross-linking reaction is described. The method takes advantage of the availability of several chemical groups on the surface of the VLPs that can be targets for specific reactions.
11:25
Targeting Cysteine Thiols for in Vitro Site-specific Glycosylation of Recombinant Proteins
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Cited by 1 •
2017
Biochemical and structural analyses of glycosylated proteins require relatively large amounts of homogeneous samples. Here, we present an efficient chemical method for site-specific glycosylation of recombinant proteins purified from bacteria by targeting reactive Cys thiols.
09:51
Cell-Based Drug Screening for Inhibitors of Autophagy Related 4B Cysteine Peptidase
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2023
Here, we describe a detailed protocol for the use of a luciferase-based reporter assay in a semi-automated, high-throughput screening format.
FAQs
The neighboring histidine acts as a catalytic partner for the active-site cysteine. By activating the cysteine thiol, it enables that sulfur-containing group to attack a peptide bond rather than remaining chemically unreactive. This partnership initiates formation of a reaction intermediate, making histidine essential to the bond-cleavage sequence and the enzyme’s biological activity.
After the cysteine attacks the peptide bond, the reaction passes through a temporary intermediate before hydrolysis is completed. This intermediate connects the initial nucleophilic attack with the final cleavage products. Following this sequence helps explain how a localized active-site event produces controlled protein degradation rather than an undefined chemical breakdown.
Cysteine proteinases can connect catalytic chemistry with broader biological outcomes because peptide-bond cleavage changes the proteins available for turnover and signaling. In this way, activity at the active site can influence processes beyond a single chemical reaction, linking molecular catalysis to regulation of cellular and tissue functions.
Their activity contributes to several distinct biological processes, including digestion, apoptosis, immune responses, and tissue remodeling. These roles show that protein cleavage can serve both maintenance and regulation: it can support protein turnover, participate in programmed cell death, influence host defense, and help modify tissues during biological change.
Finding these enzymes in organisms ranging from parasites to humans allows researchers to examine shared catalytic principles in different biological settings. Their distribution also connects enzyme activity with disease mechanisms, including infection and disorders involving inflammation, cancer, or abnormal tissue regulation. This breadth makes them relevant to both basic and biomedical research.
Selective inhibitors provide tools for examining what happens when particular cysteine proteinase activities are reduced or blocked. Studying those effects can clarify enzyme contributions to infection, inflammation, cancer, and other disorders. Inhibitor research therefore supports both mechanistic investigation and the broader development of approaches aimed at understanding disease-related protein turnover and signaling.