Practice question

SECIS binding protein 2 SBP2 is limiting factor for selenoprotein synthesis in vertebrates containing L7Ae RNA-binding module, SECIS interaction domain, and ribosome-binding Lys-rich segment. SBP2 specifically distinguishes functional SECIS kink-turn from similar hairpins, binding with nanomolar affinity to conserved AUGA core. Upon recognition, SBP2 docks onto 40S ribosomal subunit via ribosomal protein eS31, coordinating recruitment of EFSec and Sec-tRNASec complex to decoding center. Human mutations in SBP2 cause impaired selenoprotein production, thyroid hormone metabolism defects, and growth retardation. Unlike bacterial SelB directly binding SECIS, eukaryotic separation allows additional regulation, tissue specificity, and selenium status integration via feedback mechanisms.