title: Cyclization of the N-terminal X-Asn-Gly motif during sample preparation for bottom-up proteomics.
abstract: We, herein, report a novel -17 Da peptide modification corresponding to an N-terminal cyclization of peptides possessing the N-terminal motif of X-Asn-Gly. The cyclization occurs spontaneously during sample preparation for bottom-up proteomics studies. Distinct from the two well-known N-terminal cyclizations, cyclization of N-terminal glutamine and S-carbamoylmethylcysteine, it is dependent on pH instead of [NH(4)(+)]. The data set from our recent study on large-scale N(α)-modified peptides revealed a sequence requirement for the cyclization event similar to the well-known deamidation of Asn to isoAsp and Asp. Detailed analysis using synthetic peptides confirmed that the cyclization forms between the N-terminus and its neighboring Asn residue, and the reaction shares the same succinimide intermediate with the Asn deamidation event. As a result, we, here, propose a molecular mechanism for this specific cyclization.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Southern Denmark, 5230 Odense, Denmark.
authors.forename: Xumin
authors.initials: X
authors.lastname: Zhang
authors.forename: Peter
authors.initials: P
authors.lastname: Højrup
mesh_terms: D000595:Amino Acid Sequence; D001216:Asparagine / Q000737:chemistry; D003500:Cyclization; D004151:Dipeptides / Q000737:chemistry*; D005998:Glycine / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010456:Peptides, Cyclic / Q000737:chemistry*; D040901:Proteomics / Q000379:methods*
chemical_list: D004151:Dipeptides; D010456:Peptides, Cyclic; D001216:Asparagine; D005998:Glycine