The posttranslational modification of cellular proteins by ubiquitin (Ub), called ubiquitylation, is indispensable for the normal growth and development of eukaryotic organisms. In order to conduct studies that elucidate the precise mechanistic roles for Ub, access to site-specifically and homogenously ubiquitylated proteins and peptides is critical. However, the low abundance, heterogeneity, and dynamic nature of protein ubiquitylation are significant limitations toward such studies. Here we provide a facile expressed protein ligation method that does not require specialized apparatus and permits the rapid semisynthesis of ubiquitylated peptides by using the atom-efficient ligation auxiliary 2-aminooxyethanethiol.
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http://dx.doi.org/10.1007/978-1-0716-0434-2_14 | DOI Listing |
Nat Chem
November 2024
Division of Genetics, Department of Medicine, Brigham and Women's Hospital, Boston, MA, USA.
Lys ubiquitination is catalysed by E3 ubiquitin ligases and is central to the regulation of protein stability and cell signalling in normal and disease states. There are gaps in our understanding of E3 mechanisms, and here we use protein semisynthesis, chemical rescue, microscale thermophoresis and other biochemical approaches to dissect the role of catalytic base/acid function and conformational interconversion in HECT-domain E3 catalysis. We demonstrate that there is plasticity in the use of the terminal side chain or backbone carboxylate for proton transfer in HECT E3 ubiquitin ligase reactions, with yeast Rsp5 orthologues appearing to be possible evolutionary intermediates.
View Article and Find Full Text PDFBioorg Chem
September 2024
Department of Biotechnology, University of Verona, 37134 Verona, Italy. Electronic address:
Protein semisynthesis approaches are key for gaining insights into the effects of post-translational modifications (PTMs) on the structure and function of modified proteins. Among PTMs, ubiquitination involves the conjugation of a small protein modifier to a substrate amino acid residue and is unique in controlling a variety of cellular processes. Interest has grown in understanding the role of ubiquitination in neurodegenerative conditions, including tauopathies.
View Article and Find Full Text PDFbioRxiv
May 2024
Department of Biochemistry, University of Wisconsin - Madison, Madison, WI, USA 53706.
In biological systems, ATP provides an energetic driving force for peptide bond formation, but protein chemists lack tools that emulate this strategy. Inspired by the eukaryotic ubiquitination cascade, we developed an ATP-driven platform for C-terminal activation and peptide ligation based on MccB, a bacterial ancestor of ubiquitin-activating (E1) enzymes that natively catalyzes C-terminal phosphoramidate bond formation. We show that MccB can act on non-native substrates to generate an -AMPylated electrophile that can react with exogenous nucleophiles to form diverse C-terminal functional groups including thioesters, a versatile class of biological intermediates that have been exploited for protein semisynthesis.
View Article and Find Full Text PDFJ Am Chem Soc
August 2023
School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, China.
With the growing popularity of serine/threonine ligation (STL) and cysteine/penicillamine ligation (CPL) in chemical protein synthesis, facile and general approaches for the preparation of peptide salicylaldehyde (SAL) esters are urgently needed, especially those viable for obtaining expressed protein SAL esters. Herein, we report the access of SAL ester surrogates from peptide hydrazides (obtained either synthetically or recombinantly) via nitrite oxidation and phenolysis by 3-(1,3-dithian-2-yl)-4-hydroxybenzoic acid (SAL(-COOH)). The resulting peptide SAL(-COOH) esters can be activated to afford the reactive peptide SAL(-COOH) esters for subsequent STL/CPL.
View Article and Find Full Text PDFMethods
July 2023
Department of Chemistry, University of Washington, Seattle, WA 98195, United States. Electronic address:
Histone post-translational modifications (PTMs) on lysine residues, including methylation, ubiquitylation, and sumoylation, have been studied using semisynthetic histones reconstituted into nucleosomes. These studies have revealed the in vitro effects of histone PTMs on chromatin structure, gene transcription, and biochemical crosstalk. However, the dynamic and transient nature of most enzyme-chromatin interactions poses a challenge toward identifying specific enzyme-substrate interactions.
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