Crystal structure of Arabidopsis thaliana cytidine deaminase

Cytidine deaminase (CDA) catalyzes the (deoxy)cytidine deamination to (deoxy)uridine, which involves in the catabolic and salvage pathways of pyrimidine nucleotides in plants. CDA serves as a prototype of the cytidine deaminase superfamily that contains a number of RNA editing enzymes. Arabidopsis thaliana has only one functional CDA, AtCDA1. We solved the crystal structures of AtCDA1, which is a dimeric zinc-containing enzyme and each protomer consists of an N-terminal zinc-binding catalytic domain and a C-terminal non-catalytic domain. Both domains adopt a typical α/β/α sandwich fold. In vitro biochemical assays showed that the ribose moiety of cytidine is required for ligand binding, and structural analyses revealed a conserved catalytic mechanism is adopted by AtCDA1.

Keywords: Catalytic mechanism; Crystallography; Pyrimidine metabolism; RNA editing.