[4][5][6] Cytoplasmic ribosomes, organelles that catalyze protein synthesis, consist of a small 40S subunit and a large 60S subunit.

Together these subunits are composed of 4 RNA species and approximately 80 structurally distinct proteins.

This gene encodes ribosomal protein S4, a component of the 40S subunit.

The 3 isoforms encoded by these genes are not identical, but appear to be functionally equivalent.

It has been suggested that haploinsufficiency of the ribosomal protein S4 genes plays a role in Turner syndrome; however, this hypothesis is controversial.