Disease relevance of AT4G18930

• The structure is similar to those of the cyclic phosphodiesterase from Arabidopsis thaliana and the 2'-5' RNA ligase from Thermus thermophilus, placing CNP in the superfamily of 2H phosphodiesterases that contain two tetrapeptide HX(T/S)X motifs [1].

High impact information on AT4G18930

• CPDase hydrolyzes ADP-ribose 1",2"-cyclic phosphate (Appr>p), a product of the tRNA splicing reaction, to the monoester ADP-ribose 1"-phosphate (Appr-1"p) [2].
• Based on the crystal structure and on recent mutagenesis studies of a homologous CPDase from Saccharomyces cerevisiae, we propose an enzymatic mechanism that employs the nucleophilic attack of a water molecule activated by one of the active site histidines [2].
• CPDase possesses six cysteine residues, four of which are involved in forming two intra-molecular disulfide bridges [3].
• The semireduced state of CPDase also enabled co-crystallization with a putative inhibitor of its enzymatic activity, 2',3'-cyclic uridine vanadate [3].
• Indirect immunofluorescence, performed with transfected protoplasts, showed that CPDase is localized in the cytoplasm [4].

Biological context of AT4G18930

• Using the consensus phosphodiesterase signature, we have identified the yeast Saccharomyces cerevisiae open reading frame YGR247w as encoding CPDase [5].

Associations of AT4G18930 with chemical compounds

• Comparison of the previously cloned CPDase from Arabidopsis with proteins having related cyclic phosphodiesterase or RNA ligase activities revealed two histidine-containing tetrapeptides conserved in these enzyme families [5].

Analytical, diagnostic and therapeutic context of AT4G18930

• The enzymatic activity of wild type CPDase (A. thaliana) as well as of four mutants were characterized by isothermal titration calorimetry and the results prove the requirement of all four residues of the previously identified tandem signature motif for the catalytic function [6].
• Site-directed mutagenesis of individual amino acids within the two conserved tetrapeptides showed that H(40)and H(150)residues are essential for CPDase activity [5].

References