SRP9 is a key component of the signal recognition particle (SRP) complex that mediates cotranslational targeting of secretory and membrane proteins to the endoplasmic reticulum 1. Together with SRP14, SRP9 forms a heterodimeric subunit that constitutes the elongation arrest domain of SRP and is required for SRP RNA binding 2. The SRP9/SRP14 complex binds with high affinity to the scaffolding 7SL RNA and primate-specific Alu RNAs through conserved structural motifs, with human SRP9/14 showing higher binding affinity than mouse homologs to various Alu-like RNAs 3. Beyond its canonical SRP function, SRP9 plays diverse regulatory roles in Alu RNA diversification, maturation, and function 2. Disease relevance includes identification as a febrile seizure susceptibility gene, where reduced SRP9 expression decreases seizure susceptibility by affecting glutamate receptor trafficking and reducing AMPA/NMDA currents 1. Additionally, SRP9 is upregulated in colorectal cancer tissues, showing predominantly cytoplasmic localization in neoplastic cells 4. The protein is also found in extracellular vesicles, suggesting roles in cellular communication 5. Clinical significance includes potential biomarker applications in cancer diagnosis and seizure susceptibility assessment.