A Non-Functional Carbon Dioxide-Mediated Post-Translational Modification on Nucleoside Diphosphate Kinase of Arabidopsis thaliana .

The carbamate post-translational modification (PTM), formed by the nucleophilic attack of carbon dioxide by a dissociated lysine epsilon-amino group, is proposed as a widespread mechanism for sensing this biologically important bioactive gas. Here, we demonstrate the discovery and in vitro characterization of a carbamate PTM on K9 of Arabidopsis nucleoside diphosphate kinase ( At NDK1). We demonstrate that altered side chain reactivity at K9 is deleterious for At NDK1 structure and catalytic function, but that CO 2 does not impact catalysis. We show that nucleotide substrate removes CO 2 from At NDK1, and the carbamate PTM is functionless within the detection limits of our experiments. The At NDK1 K9 PTM is the first demonstration of a functionless carbamate. In light of this finding, we speculate that non-functionality is a possible feature of the many newly identified carbamate PTMs.