Structural insights to the RRM-domain of the glycine-rich RNA-binding protein from Sorghum bicolor and its role in cold stress tolerance in E. coli

Sorghum bicolor Glycine-rich RNA-binding protein (SbGRBP), exhibit the ability to bind both single-stranded and double-stranded DNA. The expression of SbGRBP is regulated by heat stress, with the protein localizing to the nucleus and cytosol. The present study delves into the structure and ssDNA binding ability of its truncated version (SbGRBP1-119) which lacks glycine rich domain (GR). This protein has the ability to bind ssDNA Using Nuclear Magnetic Resonance (NMR) spectroscopy, we have revealed the secondary structure of SbGRBP1-119, highlighting the typical configuration of GRBPs with four beta-sheets and two alpha-helices. Notably, we found two additional alpha-helices at the N-terminal region that seem to interact with ssDNA, a novel observation for GRBPs. Key residues crucial for ssDNA binding were identified, suggesting a specific interaction with the oligonucleotide sequence 5'-TTCTGG-3 '. Preliminary assays hinted that SbGRBP1-119 might bolster E. coli resilience to cold stress, indicating a potential chaperone-like role under stress conditions. This study sheds light on the structural basis of SbGRBP1-119's interaction with nucleic acids, deepening our understanding about the role of GRBPs' in RNA metabolism and regulation.