Functional ubiquitin conjugates with lysine-epsilon-amino-specific linkage by thioether ligation of cysteinyl-ubiquitin peptide building blocks.
The modification of ubiquitin to defined oligo-ubiquitinated conjugates has received considerable interest due to the finding that isomeric oligo-ubiquitin conjugates exhibit distinct differences in their biochemical functions, depending on the specific lysine-epsilon-amino linkage used for conjugate formation. Here, we report the design and development of a thioether linkage-based approach for the synthesis of oligo-ubiquitin conjugates with lysine-specific branching by thioether ligation of a linear ubiquitin peptide containing a C-terminal cysteine residue as the "donor" component, with a corresponding lysine-epsilon-amino-branched haloacyl-activated ubiquitin "acceptor" peptide. This approach was successfully used for the synthesis of a lysine-63-linked diubiquitin conjugate by ligation of the modified ubiquitin(1-52)-Cys- donor peptide to the N-terminal Arg-54 residue of the branched Lys-63-linked acceptor peptide, ubiquitin(54-76)(2). Advantages of the present approach are as follows: (i) the conjugation reaction is performed in solution using suitable preformed donor ubiquitin peptides with a C-terminal Cys residue, and (ii) different corresponding N-chloroacetylated ubiquitin acceptor peptides containing the branched Lys residue are employed, providing broad applicability to the preparation of isomeric oligo-ubiquitin conjugates. The Lys-63-diubiquitin conjugate 7 described here was purified by semipreparative HPLC, and its structure and homogeneity ascertained by HPLC and high-resolution MALDI and electrospray-mass spectrometry. CD spectra and molecular modeling indicate a conformationally stable structure of the conjugate with spatial separation of the ubiquitin parts of the Lys-63 linkage. Moreover, the activity of the thioether-linked diubiquitin conjugate was ascertained by in vitro autoubiquitination assay. These results indicate the feasibility of this approach for the preparation of functional oligo-ubiquitin conjugates.
Jung
Ji Eun
JE
Department of Chemistry, Laboratory of Analytical Chemistry, University of Konstanz, Universitatsstrasse 10, D-78457 Konstanz, Germany.
Wollscheid
Hans-Peter
HP
Marquardt
Andreas
A
Manea
Marilena
M
Scheffner
Martin
M
Przybylski
Michael
M
D000107:Acetylation; D000588:Amines / Q000737:chemistry*; D000595:Amino Acid Sequence; D002942:Circular Dichroism; D003545:Cysteine / Q000737:chemistry*; D015195:Drug Design; D007536:Isomerism; D008239:Lysine / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010455:Peptides / Q000737:chemistry*; D011487:Protein Conformation; D013379:Substrate Specificity; D013440:Sulfides / Q000737:chemistry*; D025801:Ubiquitin / Q000737:chemistry* / Q000235:genetics; D054875:Ubiquitination
D000588:Amines; D010455:Peptides; D013440:Sulfides; D025801:Ubiquitin; D008239:Lysine; D003545:Cysteine