Ubiquitin-Mimicking Peptides Transfer Differentiates by E1 and E2 Enzymes

Area of Science:

• Biochemistry
• Molecular Biology
• Proteomics

Background:

• Ubiquitin and ubiquitin-like proteins (UBLs) are vital post-translational modifiers in eukaryotes.
• These proteins utilize an E1-E2-E3 enzymatic cascade for conjugation to target proteins, altering their functions.
• Known UBLs include Nedd8, SUMO, ISG15, and Atg8, all sharing a conserved β-grasp fold and C-terminal motif.

Purpose of the Study:

• To investigate if C-terminal UBL-mimicking peptides, when fused to proteins, retain reactivity with pathway enzymes.
• To explore the role of protein frame structure in the recognition of E2 enzymes with peptide-fused proteins.

Main Methods:

• Bioinformatic screening identified eight proteins with the conserved UBL C-terminal motif.
• Synthesized C-terminal peptides were tested for reactivity with the ubiquitin E1 enzyme (Ube1).
• Reactive peptides were fused to ubiquitin, peptidyl carrier protein (PCP), and native protein frames for further enzymatic assays.

Main Results:

• Three synthesized peptides exhibited reactivity with the E1 enzyme Ube1.
• Peptide-fused proteins on ubiquitin and PCP frames showed reactivity with Ube1.
• However, PCP-peptide fusions lost reactivity with the E2 enzyme UbcH7, indicating frame-dependent E2 recognition.

Conclusions:

• The C-terminal sequence of UBL-mimicking peptides is not solely sufficient for E2 enzyme recognition.
• The overall structure of the protein frame fused to the peptide significantly influences E2 enzyme interaction.
• This suggests a complex interplay between peptide motif and protein context in ubiquitinylation pathways.