May act as a molecular switch during maturation of the 40S ribosomal subunit in the nucleolus. The depletion of BMS1 interferes with processing of the 35S pre-rRNA at sites A0, A1, and A2, and the formation of 40S subunits. Associates with RCL1. Belongs to the TRAFAC class translation factor GTPase superfamily. Bms1-like GTPase family. BMS1 subfamily.