Structural basis of the specific interactions of GRAS family proteins

The plant-specific GAI-RGA-and-SCR (GRAS) family of proteins function as transcriptional regulators and play critical roles in development and signalling. Recent structural studies have shed light on the molecular functions at the structural level. The conserved GRAS domain comprises an α-helical cap and α/β core subdomains. The α-helical cap mediates head-to-head heterodimerization between SHR and SCR GRAS domains. This type of dimerization is predicted for the NSP1-NSP2 heterodimer and DELLA proteins such as RGA and SLR1 homodimers. The α/β core subdomain possesses a hydrophobic groove formed by surface α3- and α7-helices and mediates protein-protein interactions. The groove of the SHR GRAS domain accommodates the zinc fingers of JKD, a BIRD/IDD family transcription factor, while the groove of the SCL7 GRAS domain mediates the SCL7 homodimerization.