Ribosome Recycling Factor

mitochondrial ribosome recycling factor
Identifiers
Symbol	MRRF
Entrez	92399
HUGO	7234
OMIM	604602
RefSeq	NM_138777
UniProt	Q96E11
Other data
Locus	Chr. 9 q32-q34.1

Ribosome Recycling Factor (RRF) is a protein found in bacterial cells as well as eukaryotic organelles, specifically and chloroplasts. It functions to recycle ribosomes after completion of protein synthesis.

The ribosome recycling factor was discovered in the early 1970s by the work of Akira Kaji and Akikazu Hiroshima at the University of Pennsylvania. Their work described the requirement for two protein factors to release ribosomes from mRNA. These two factors were identified as RRF, an unknown protein until then, and Elongation Factor G (EF-G), a protein already identified and known to function in protein synthesis. RRF was originally called Ribosome Releasing Factor but is now called Ribosome Recycling Factor.

Recent evidence suggests RRF may accomplish the recycling of ribosomes by splitting ribosomes into subunits, thereby releasing the bound mRNA.

The crystal structure of RRF was first determined by X-ray diffraction in 1999. The most striking revelation was that RRF is a near-perfect structural mimic of tRNA, in both size and dimensions. One view of RRF can be seen here.

Despite the tRNA-mimicry, RRF binds to ribosomes quite differently from the way tRNA does. It has been suggested that ribosomes bind proteins (or protein domain) of similar shape and size to tRNA, and this, rather than function, explains the observed structural mimicry.

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