RPS4 plays a critical role in the core assembly of the small ribosomal subunit with a KOW motif at its C-terminal. RPS4 also acts as a general transcription antiterminator factor and regulates ribosomal RNA expression level. KOW domain is known as an RNA-binding motif that is shared so far among some families of ribosomal proteins, the essential bacterial transcriptional elongation factor NusG, the eukaryotic chromatin elongation factor Spt5, the higher eukaryotic KIN17 proteins and Mtr4. RPS4 deficiency in human has been associated with Turner syndrome. Archeae RPS4 (RPS4e) showed substantial identity to the eukaryotic equivalents RPS4, but the archaeal proteins formed a different complex from the eukaryotic proteins.
Jiyao W et al.(2023). "The conserved domain database in 2023.",