PROSITE documentation PDOC50985

GRAS domain profile

GRAS proteins are a family of plant-specific transcriptional regulators named after GAI, RGA and SCR, the first three of its members isolated. Their functions are related to diverse processes involved in plant growth and development. These include gibberellic acid signaling , shoot meristem maintenance, root radial patterning, light signal transduction, male gametogenesis, axillary meristem formation, and nodule morphogenesis. GRAS proteins form homodimers and heterodimers with other GRAS family members and this is likely important for their transcriptional regulation function.

The major characteristic domain of GRAS proteins is the C-terminal GRAS domain, which exhibits considerable sequence similarity between GRAS proteins. The GRAS domain is typically composed of ~380 amino acids and contains five highly conserved motifs, found in the following order: leucine heptad repeat I (LRI), the VHIID motif, leucine heptad repeat II (LRII), the PFYRE motif and the SAW motif. Plant specific GRAS proteins have parallels in their motif structure to the animal Signal Transducers and Activators of Transcription (STAT) family of proteins which suggests also some parallels in their functions [1,2,3,4,5].

The GRAS domain contains an eight-stranded mixed β-sheet (B1-B9) with an accessory small β-strand B6 and 12 α-helices (A1-A12) as well as five 3(10) helices (see <PDB:5HYZ>). The GRAS domain is composed of cap and core subdomains. The cap subdomain at the top is composed of a helical bundle formed by N-terminal α-helices A1, A2, and A3 from the LRI motif and a noncontiguous helical bundle insert (A9, A10 from the PFYRE motif. The core subdomain is much larger, forming a α/β/α three-layer sandwiched Rossmann fold-like structure. The central β-sheet is formed by parallel β-strands B1-B5 and extended by antiparallel β-strands B9, B7 and B8. B6 is also a small accessory β-strand. Flanking each side of the central β-sheet are two helical layers formed by small 3(10) helices, α-helices A8, A11, and A5, A6, A7, and A12, respectively. The orientation of the top cap subdomain helical bundle is approximately perpendicular to the bottom α/ β/α sandwiched three-layer core. The two subdomains are linked by a long loop and helix A4 [5].

Some proteins known to contain a GRAS domain are listed below:

• Arabidopsis thaliana SCARECROW (SCR) protein. It regulates asymmetric cell divisions of cortex/endodermal initial cells during root development.
• Arabidopsis thaliana SCARECROW-LIKE (SCL) protein.
• Arabidopsis thaliana GIBBERELLIN-ACID INSENSITIVE (GAI) and REPRESSOR OF GA1 (RGA), two closely related proteins involved in gibberellin signaling.
• Arabidopsis thaliana SHORT ROOT (SHR) protein. It is necessary for cell division and endodermis specification.
• Arabidopsis thaliana PAT1 protein. It inhibits light signaling via the phytochrome A (phyA).
• LATERAL SUPPRESSOR (LS), a protein from tomato that controls the formation of lateral branches during vegetative development.
• Nodulation-signaling pathway 1 and 2 proteins (NSP1-NSP2) from Medicago truncatula. They play a role in DNA promoter regulation for nodulation signaling.

The profile we developed covers the whole GRAS domain.