Three-dimensional placement of the conserved 530 loop of 16 S rRNA and of its neighboring components in the 30 S subunit

Nucleotides 518-533 form a loop in ribosomal 30 S subunits that is almost u niversally conserved. Both biochemical and genetic evidence clearly implica te the 530 loop in ribosomal function, with respect both to the accuracy co ntrol mechanism and to tRNA binding. Here, building on earlier work, we ide ntify proteins and nucleotides (or limited sequences) site-specifically pho tolabeled by radioactive photolabile oligoDNA probes targeted toward the 53 0 loop of 30 S subunits. The probes we employ are complementary to 16 S rRN A nucleotides 517-527, and have aryl azides attached to nucleotides complem entary to nucleotides 518, 522, and 525-527, positioning the photogenerated nitrene a maximum of 19-26 Angstrom from the complemented rRNA base. The c rosslinks obtained are used as constraints to revise an earlier model of 30 S structure, using the YAMMP molecular modeling package, and to place the 530 loop region within that structure. (C) 1999 Academic Press.