Crystal structure of Thermotoga maritima ribosome recycling factor: a tRNA mimic.

Ribosome recycling factor (RRF), together with elongation factor G (EF-G), catalyzes recycling of ribosomes after one round of protein synthesis. The crystal structure of RRF was determined at 2.55 angstrom resolution. The protein has an unusual fold where domain I is a long three-helix bundle and domain II is a three-layer beta/alpha/beta sandwich. The molecule superimposes almost perfectly with a transfer RNA (tRNA) except that the amino acid-binding 3' end is missing. The mimicry suggests that RRF interacts with the posttermination ribosomal complex in a similar manner to a tRNA, leading to disassembly of the complex. The structural arrangement of this mimicry is entirely different from that of other cases of less pronounced mimicry of tRNA so far described.