Crystal Structure of the Ribosome at 5.5 Å Resolution

TLDR

We describe the crystal structure of the complete Thermus thermophilus 70 S ribosome with bound mRNA and tRNAs at 5.5 Å resolution. The electron density map at 5.5 Å resolves all rRNA chains, the A‑, P‑, and E‑site tRNAs, and most ribosomal proteins, revealing an RNA‑dominated intersubunit interface with peripheral proteins, tRNA contacts that explain tRNA structural conservation, and juxtaposition of tRNAs with intersubunit bridges suggesting coupled subunit movements during translocation.

Abstract

We describe the crystal structure of the complete Thermus thermophilus 70 S ribosome containing bound messenger RNA and transfer RNAs (tRNAs) at 5.5 angstrom resolution. All of the 16 S , 23 S , and 5 S ribosomal RNA (rRNA) chains, the A-, P-, and E-site tRNAs, and most of the ribosomal proteins can be fitted to the electron density map. The core of the interface between the 30 S small subunit and the 50 S large subunit, where the tRNA substrates are bound, is dominated by RNA, with proteins located mainly at the periphery, consistent with ribosomal function being based on rRNA. In each of the three tRNA binding sites, the ribosome contacts all of the major elements of tRNA, providing an explanation for the conservation of tRNA structure. The tRNAs are closely juxtaposed with the intersubunit bridges, in a way that suggests coupling of the 20 to 50 angstrom movements associated with tRNA translocation with intersubunit movement.