A structural view of the conserved domain of rice stress-responsive NAC1.

The importance of NAC (named as NAM, ATAF1, 2, and CUC2) proteins in plant development, transcription regulation and regulatory pathways involving protein-protein interactions has been increasingly recognized. We report here the high resolution crystal structure of SNAC1 (stress-responsive NAC) NAC domain at 2.5 Å. Although the structure of the SNAC1 NAC domain shares a structural similarity with the reported structure of the ANAC NAC1 domain, some key features, especially relating to two loop regions which potentially take the responsibility for DNA-binding, distinguish the SNAC1 NAC domain from other reported NAC structures. Moreover, the dimerization of the SNAC1 NAC domain is demonstrated by both soluble and crystalline conditions, suggesting this dimeric state should be conserved in this type of NAC family. Additionally, we discuss the possible NAC-DNA binding model according to the structure and reported biological evidences.