Abstract
BackgroundThe N-terminal protein processing mechanism (NPM) including N-terminal Met excision (NME) and N-terminal acetylation (Nα-acetylation) represents a common protein co-translational process of some eukaryotes. However, this NPM occurred in woody plants yet remains unknown.Methodology/Principal FindingsTo reveal the NPM in poplar, we investigated the Nα-acetylation status of poplar proteins during dormancy by combining tandem mass spectrometry with TiO2 enrichment of acetylated peptides. We identified 58 N-terminally acetylated (Nα-acetylated) proteins. Most proteins (47, >81%) are subjected to Nα-acetylation following the N-terminal removal of Met, indicating that Nα-acetylation and NME represent a common NPM of poplar proteins. Furthermore, we confirm that poplar shares the analogous NME and Nα-acetylation (NPM) to other eukaryotes according to analysis of N-terminal features of these acetylated proteins combined with genome-wide identification of the involving methionine aminopeptidases (MAPs) and N-terminal acetyltransferase (Nat) enzymes in poplar. The Nα-acetylated reactions and the involving enzymes of these poplar proteins are also identified based on those of yeast and human, as well as the subcellular location information of these poplar proteins.Conclusions/SignificanceThis study represents the first extensive investigation of Nα-acetylation events in woody plants, the results of which will provide useful resources for future unraveling the regulatory mechanisms of Nα-acetylation of proteins in poplar.
Highlights
The N-terminal protein processing mechanism (NPM) represents a common protein modification that occurs in eukaryotes, and primarily involves the co-translational processes of N-terminal Met excision (NME) and N-terminal acetylation (Na-acetylation) [1,2,3,4]
Experimental data have shown that, in higher eukaryotes, MAP1s are found in mitochondria, plastids, and the cytoplasm, whereas MAP2s are found in the cytoplasm, suggesting that NME occurs in all compartments where de novo protein synthesis occurs [1,5,10]
These 58 proteins were divided into two groups: (i) the NME-independent Na-acetylation group, where the N-terminal Met residue is retained and subsequently acetylated; and (ii) the NME-dependent Na-acetylation group, where the N-terminal iMet residue is removed and acetylation occurs at the exposed residue located at position two
Summary
The N-terminal protein processing mechanism (NPM) represents a common protein modification that occurs in eukaryotes, and primarily involves the co-translational processes of N-terminal Met excision (NME) and N-terminal acetylation (Na-acetylation) [1,2,3,4]. NME of the plastid-encoded proteins requires MAP activity and peptide deformylase (PDF) activity [7] The latter enzymatic activity is required for the removal of the Fo groups, thereby unmasking the amino group of the first Met and allowing the subsequent action of MAP [1,5,8]. The N-terminal protein processing mechanism (NPM) including N-terminal Met excision (NME) and N-terminal acetylation (Na-acetylation) represents a common protein co-translational process of some eukaryotes. This NPM occurred in woody plants yet remains unknown
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