Ribosome recycling factor

Ribosome recycling factor or ribosome release factor (RRF) is a protein found in bacterial cells as well as eukaryotic organelles, specifically mitochondria and chloroplasts. It functions to recycle ribosomes after completion of protein synthesis (bacterial translation). In humans, the mitochrondrial version is coded by the MRRF gene.

Ribosome recycling factor
Identifiers
Symbol	RRF
Pfam	PF01765
InterPro	IPR002661
CATH	1ek8
SCOP2	1ek8 / SCOPe / SUPFAM
CDD	cd00520
Available protein structures: Pfam   structures / ECOD   PDB RCSB PDB; PDBe; PDBj PDBsum structure summary

MRRF
Identifiers
Aliases	MRRF, MRFF, MTRRF, RRF, mitochondrial ribosome recycling factor
External IDs	OMIM: 604602; MGI: 1915121; HomoloGene: 12203; GeneCards: MRRF; OMA:MRRF - orthologs
Gene location (Human) Chr. Chromosome 9 (human)[1] Band 9q33.2 Start 122,264,603 bp[1] End 122,331,337 bp[1]
Gene location (Mouse) Chr. Chromosome 2 (mouse)[2] Band 2|2 B Start 36,026,401 bp[2] End 36,080,659 bp[2]
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in rectum left testis right testis mucosa of transverse colon right uterine tube gastrocnemius muscle right lobe of liver left lobe of thyroid gland right lobe of thyroid gland apex of heart Top expressed in tail of embryo genital tubercle interventricular septum endothelial cell of lymphatic vessel Paneth cell spermatid external carotid artery condyle muscle of thigh left lobe of liver More reference expression data BioGPS n/a
Gene ontology Molecular function ribosomal large subunit binding Cellular component mitochondrial matrix mitochondrion Biological process ribosome disassembly protein biosynthesis mitochondrial translational termination Sources:Amigo / QuickGO
Orthologs Species Human Mouse Entrez 92399 67871 Ensembl ENSG00000148187 ENSMUSG00000026887 UniProt Q96E11 Q9D6S7 RefSeq (mRNA) NM_001173512 NM_138777 NM_199176 NM_199177 NM_001346339 NM_001346341 NM_001346343 NM_001346345 NM_001346347 NM_026422 RefSeq (protein) NP_001166983 NP_001333268 NP_001333270 NP_001333272 NP_001333274 NP_001333276 NP_620132 NP_954646 NP_080698 Location (UCSC) Chr 9: 122.26 – 122.33 Mb Chr 2: 36.03 – 36.08 Mb PubMed search [3] [4]
Wikidata
View/Edit Human View/Edit Mouse

Discovery

The ribosome recycling factor was discovered in the early 1970s by the work of Akira Kaji and Akikazu Hiroshima at the University of Pennsylvania.^[5][6][7][8] 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.

Function

RRF accomplishes the recycling of ribosomes by splitting ribosomes into subunits, thereby releasing the bound mRNA. This also requires the participation of EF-G (GFM2 in humans).^[9] Depending on the tRNA, IF1–IF3 may also perform recycling.^[10]

Loss of RRF function

• In Bacteria (specifically Escherichia coli), loss of the gene encoding RRF is deleterious.^[11] This makes RRF a possible target for new antibacterial drugs.
• Yeast mitochondrial RRF (mtRRF) is encoded by a gene in the cell nucleus. Loss of function of this gene leads to mitochondrial genome instability and respiratory incompetence.^[12]

Structure and binding to ribosomes

The crystal structure of RRF was first determined by X-ray diffraction in 1999.^[13] 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.^[14] 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.

See also

• Ribosome
• Translation (genetics)
• Eukaryotic release factors