Escherichia coliproteinY (pY) binds to the small ribosomal subunit and stabilizes ribosomes against dissociation when bacteria experience environmental stress. pY inhibits trans-lationin vitro,most probably by interferingwith the binding of the aminoacyl-tRNA to the ribosomal A site. Such a translational arrest may mediate overall adaptation of cells to environmental conditions. We have determined the 3D solution structure of a 112-residue pY and have studied its backbone dynamic by NMRspectroscopy. .
