Ribosome structure: localization of N6,N6-dimethyladenosine by electron microscopy of a ribosome-antibody complex.

Abstract

Antibodies to the minor nucleoside N6,N6-dimethyladenosine were used to map a unique location of the nucleoside in the small subunit of the Escherichia coli ribosome. Antibodies were induced in rabbits by a nucleoside-bovine albumin conjugate and were highly specific for the dimethyladenosine hapten. The antibodies interacted with 30S ribosomal subunits from strain PR7, but not with subunits from its mutant strain TPR201, which is resistant to kasugamycin and lacks the 2 successive residues of dimethyladenosine normally found near the 3''-end of E. coli 16S rRNA. Electron micrographs of strain PR7 subunits, crosslinked by single Ig[immunoglobulin]G molecules, show a single binding site on the surface of the ribosome. This binding site is consistent with observations relating the 3''-end of the rRNA, binding of initiation factor IF-3 and mRNA, and mapping of specific ribosomal proteins.