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C-terminal cyclic imides are posttranslational modifications (PTMs) on proteins that are recognized and removed by the E3 ligase substrate adapter cereblon (CRBN). Despite the observation of these modifications across the proteome by mass spectrometry-based proteomics, an orthogonal and generalizable method to visualize the C-terminal cyclic imide would enhance detection, sensitivity, and throughput of endogenous CRBN substrate characterization. Here, we develop an antibody-like reagent, termed "cerebody," for visualizing and enriching C-terminal cyclic imide-modified proteins. We describe the engineering of CRBN derivatives to produce cerebody and use it to identify CRBN substrates by western blot and enrichment from whole-cell and tissue lysates. CRBN substrates identified by cerebody enrichment are mapped, validated, and further characterized for dependence on the C-terminal cyclic imide modification. These methods will accelerate the characterization of endogenous CRBN substrates and their regulation.
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http://dx.doi.org/10.1016/j.chembiol.2025.07.002 | DOI Listing |
Acc Chem Res
August 2025
Laboratory of Catalysis and Organic Synthesis, Ecole Polytechnique Fédérale de Lausanne, EPFL SB ISIC LCSO, BCH 4306, 1015 Lausanne, Switzerland.
ConspectusAlkynes are one of the most fundamental functional groups in organic synthesis due to the versatile chemistry of the triple bond, their unique rigid structure, and their use in bioconjugation. The introduction of alkynes onto organic molecules traditionally relies on nucleophilic activation, often requiring strong bases or metal catalysts. These conditions, however, restrict applications involving biomolecules such as peptides and proteins due to functional group incompatibility.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
August 2025
Department of Chemistry, The University of Utah, Salt Lake City, UT 84112.
Disulfide bonds stabilize many bioactive peptides, but their susceptibility to reduction under physiological conditions limits broad applicability in biotechnology. PapB is a promiscuous radical -adenosyl-L-methionine enzyme that is involved in the maturation of PapA, which is a ribosomally produced and posttranslationally modified polypeptide. PapB introduces six thioether linkages between internal Cys residues and carbon atom that is α to the side-chain carboxylate of Asp/Glu residues C-terminal to the Cys residues.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
August 2025
Institute for Plant-Human Interface, Northeastern University, Boston, MA, 02115, USA.
DUF3328 is a protein family widely found in fungal natural product biosynthesis pathways. Although DUF3328 proteins have long been implicated in diverse modifications of inert C(sp)─H bonds, including halogenation, hydroxylation, and macrocyclization, the biochemical properties and catalytic mechanisms of DUF3328 proteins remain elusive. Here, we report the characterization of the DUF3328 protein CctR, which catalyzes C(sp)─H hydroxylation of fungal cyclic peptide cyclochlorotine.
View Article and Find Full Text PDFElife
August 2025
Department of Neurobiology and Biophysics, University of Washington, Seattle, United States.
Cyclic nucleotide-binding domain (CNBD) ion channels are vital for cellular signaling and excitability, with activation regulated by cyclic adenosine- or guanosine-monophosphate (cAMP, cGMP) binding. However, the allosteric mechanisms underlying this activation, particularly the energetics that describe conformational changes within individual domains and between domains, remain unclear. The prokaryotic CNBD channel SthK has been a useful model for better understanding these allosteric mechanisms.
View Article and Find Full Text PDFCell Chem Biol
August 2025
Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA; Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA. Electronic address:
C-terminal cyclic imides are posttranslational modifications (PTMs) on proteins that are recognized and removed by the E3 ligase substrate adapter cereblon (CRBN). Despite the observation of these modifications across the proteome by mass spectrometry-based proteomics, an orthogonal and generalizable method to visualize the C-terminal cyclic imide would enhance detection, sensitivity, and throughput of endogenous CRBN substrate characterization. Here, we develop an antibody-like reagent, termed "cerebody," for visualizing and enriching C-terminal cyclic imide-modified proteins.
View Article and Find Full Text PDF