Lysine Acetylation Is a Widespread Protein Modification for Diverse Proteins in Arabidopsis

Lysine acetylation (LysAc), a form of reversible protein posttranslational modification previously known only for histone regulation in plants, is shown to be widespread in Arabidopsis (Arabidopsis thaliana). Sixty-four Lys modification sites were identified on 57 proteins, which operate in a wide variety of pathways/processes and are located in various cellular compartments. A number of photosynthesis-related proteins are among this group of LysAc proteins, including photosystem II (PSII) subunits, light-harvesting chlorophyll a/b-binding proteins (LHCb), Rubisco large and small subunits, and chloroplastic ATP synthase (beta-subunit). Using two-dimensional native green/sodium dodecyl sulfate gels, the loosely PSII-bound LHCb was separated from the LHCb that is tightly bound to PSII and shown to have substantially higher level of LysAc, implying that LysAc may play a role in distributing the LHCb complexes. Several potential LysAc sites were identified on eukaryotic elongation factor-1A (eEF-1A) by liquid chromatography/mass spectrometry and using sequence- and modification-specific antibodies the acetylation of Lys-227 and Lys-306 was established. Lys-306 is contained within a predicted calmodulin-binding sequence and acetylation of Lys-306 strongly inhibited the interactions of eEF-1A synthetic peptides with calmodulin recombinant proteins in vitro. These results suggest that LysAc of eEF-1A may directly affect regulatory properties and localization of the protein within the cell. Overall, these findings reveal the possibility that reversible LysAc may be an important and previously unknown regulatory mechanism of a large number of nonhistone proteins affecting a wide range of pathways and processes in Arabidopsis and likely in all plants.