Discovering the N-terminal Methylome by the Repurposing of Proteomic Datasets

ABSTRACT: Protein ⍺-N-methylation is a cryptic and relatively unexplored post-translational modification involving the covalent addition of methyl groups to the free a-amino group at protein N-termini. To systematically explore the extent of ⍺-N-terminal methylation in yeast and humans, we utilized a repurposing method optimized for ⍺-N-terminome identification to take advantage of publicly accessible proteomic datasets. Searching of four datasets indicated the ⍺-N-methylation of established and novel substrates with canonical N-terminal motifs of established ⍺-N-terminal methyltransferases, NTMT1/2 for humans and Tae1 for yeast. Moreover, ⍺-N-methylation of non-canonical sequences was more prevalent than expected, suggesting unappreciated and cryptic methylation events. Analysis of the amino acid frequencies of ⍺-methylated peptides revealed enrichment of serine, alanine, proline and glycine at the first position for both yeast and human, suggesting amino acid sequence conservation is not required for some types of ⍺-methylation events. We delineated numerous amino acids in which there is evidence of competition between acetylation and methylation. We tested three potentially methylated proteins and confirmed the ⍺-N-terminal methylation of Hsp31. The other two proteins, Vma1 and Ssa3, were found to be predominantly acetylated. This study demonstrates the feasibility of reprocessing proteomic data for global ⍺-N-terminal methylome investigations.

INSTRUMENT(S):

ORGANISM(S): Saccharomyces Cerevisiae (baker's Yeast)

SUBMITTER: Panyue Chen  

LAB HEAD: Tony Hazbun

PROVIDER: PXD022833 | Pride | 2021-05-26

REPOSITORIES: Pride