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Encyclopedia > Ribosomal RNA

Ribosomal RNA (rRNA), a type of RNA synthesized in the nucleolus by RNA Pol I, is the central component of the ribosome, the protein manufacturing machinery of all living cells. The function of the rRNA is to provide a mechanism for decoding mRNA into amino acids and to interact with the tRNAs during translation by providing peptidyl transferase activity. Left: An RNA strand, with its nitrogenous bases. ... The nucleolus is contained within the cell nucleus. ... Figure 1: Ribosome structure indicating small subunit (A) and large subunit (B). ... Cells in culture, stained for keratin The cell is the structural and functional unit of all living organisms. ... The interaction of mRNA in a eukaryote cell. ... This article is about the class of chemicals. ... Transfer RNA (abbreviated tRNA) is a small RNA chain (74-93 nucleotides) that transfers a specific amino acid to a growing polypeptide chain at the ribosomal site of protein synthesis during translation. ... Translation is the second process of protein biosynthesis (part of the overall process of gene expression). ... ...


Inside the ribosome

The ribosome is composed of two subunits, named for how rapidly they sediment when subject to centrifugation. tRNA is sandwiched between the small and large subunits and the ribosome catalyzes the formation of a peptide bond between the 2 amino acids that are contained in the tRNA. Centrifugation is a process that involves the use of the centrifugal force for the separation of mixtures. ...

The ribosome also has 3 binding sites called A, P, and E.

  • The A site in the ribosome binds to an aminoacyl-tRNA (a tRNA bound to an amino acid).
  • The NH2 group of the aminoacyl-tRNA which contains the new amino acid, attacks the carboxyl group of peptidyl-tRNA (contained within the P site) which contains the last amino acid of the growing chain called peptidyl transferase reaction.
  • The tRNA that was holding on the last amino acid is moved to the E site, and what used to be the aminoacyl-tRNA is now the peptidyl-tRNA.

A single mRNA can be translated simultaneously by multiple ribosomes.

Prokaryotes vs. Eukaryotes

Both prokaryotic and eukaryotic can be broken down into two subunits (the S in 16S represents Svedberg units): A Svedberg (symbol S, sometimes Sv) is a non-SI physical unit used in ultracentrifugation. ...

Type Size Large subunit Small subunit
prokaryotic 70S 50S (5S, 23S) 30S (16S)
eukaryotic 80S 60S (5S, 5.8S, 28S) 40S (18S)

Note that the S units of the subunits cannot simply be added because they represent measures of sedimentation rate rather than of mass. The sedimentation rate of each subunit is affected by its shape, as well as by its mass. Centuries: 1st century BC - 1st century - 2nd century Decades: 0s - 10s - 20s - 30s - 40s - 50s - 60s - 70s - 80s - 90s - 100s 50 51 52 53 54 55 56 57 58 59 Sometimes the 50s is used as shorthand for the 1950s, the 1850s, or other such decades in various centuries Events... Centuries: 1st century BC - 1st century - 2nd century Decades: 20s BC - 10s BC - 0s - 10s - 20s - 30s - 40s - 50s - 60s - 70s - 80s 30 31 32 33 34 35 36 37 38 39 Sometimes the 30s is used as shorthand for the 1930s, the 1830s, or other such decades in various... 5S ribosomal RNA (5S rRNA) is a component of the large ribosomal subunit in both prokaryotes and eukaryotes. ... 5. ...


In Prokaryotes a small 30S ribosomal subunit contains the 16S rRNA. Prokaryotes are unicellular (in rare cases, multicellular) organisms without a nucleus. ...

The large 50S ribosomal subunit contains two rRNA species (the 5S and 23S rRNAs).

Bacterial 16S, 23S, and 5S rRNA genes are typically organized as a co-transcribed operon. An operon is a group of key nucleotide sequences including an operator, a common promoter, and one or more structural genes that are controlled as a unit to produce messenger RNA (mRNA). ...

There may be one or more copies of the operon dispersed in the genome (for example, Escherichia coli has seven). In biology the genome of an organism is the whole hereditary information of an organism that is encoded in the DNA (or, for some viruses, RNA). ... E. coli redirects here. ...

Archaea contains either a single rDNA operon or multiple copies of the operon.

The 3' end of the 16S rRNA (in a ribosome) binds to a sequence on the 5' end of mRNA called the Shine-Dalgarno sequence. The Shine-Dalgarno Sequence (AGGAGGU) is the signal for initiation of protein biosynthesis in bacterial mRNA. It is located 5 of the first coding AUG, and consists primarily, but not exclusively, of purines. ...


Small subunit ribosomal RNA, 5' domain taken from the Rfam database. This example is RF00177
Small subunit ribosomal RNA, 5' domain taken from the Rfam database. This example is RF00177

In contrast, Eukaryotes generally have many copies of the rRNA genes organized in tandem repeats; in humans approximately 300–400 rDNA repeats are present in five clusters (on chromosomes 13, 14, 15, 21 and 22). Image File history File links Size of this preview: 600 × 600 pixelsFull resolution (609 × 609 pixel, file size: 34 KB, MIME type: image/jpeg) All of these RFxxxxx. ... Image File history File links Size of this preview: 600 × 600 pixelsFull resolution (609 × 609 pixel, file size: 34 KB, MIME type: image/jpeg) All of these RFxxxxx. ... A theoretical ncRNA alignment from 6 species. ... Kingdoms Eukaryotes are organisms with complex cells, in which the genetic material is organized into membrane-bound nuclei. ... This article is about the biological chromosome. ...

The 18S rRNA in most eukaryotes is in the small ribosomal subunit, and the large subunit contains three rRNA species (the 5S, 5.8S and 28S rRNAs). 5S ribosomal RNA (5S rRNA) is a component of the large ribosomal subunit in both prokaryotes and eukaryotes. ... 5. ...

Mammalian cells have 2 mitochondrial (12S and 16S) rRNA molecules and 4 types of cytoplasmic rRNA (28S, 5.8S, 5S (large ribosome subunit) and 18S (small subunit)). 28S, 5.8S, and 18S rRNAs are encoded by a single transcription unit (45S) separated by 2 Internally transcribed spacer (ITS). The 45S rDNA organized into 5 clusters (each has 30-40 repeats) on the 13,14,15,21,and 22 chromosomes. These are transcribed by RNA polymerase I. 5S occurs in tandem arrays (~200-300 true 5S genes and many dispersed pseudogenes), the largest one on the chromosome 1q41-42. 5S rRNA is transcribed by RNA polymerase III.

The tertiary structure of the small subunit ribosomal RNA (SSU rRNA) has been resolved by xray crystallography [1]. The secondary structure of SSU rRNA contains 4 distinct domains -- the 5', central, 3' major and 3' minor domains. A model of the secondary structure for the 5' domain (500-800 nucleotides) is shown.


Translation is the net effect of proteins being synthesized by ribosomes, from a copy (mRNA) of the DNA template in the nucleus. One of the components of the ribosome (16s rRNA) base pairs complementary to a sequence upstream of the start codon in mRNA. Translation is the second process of protein biosynthesis (part of the overall process of gene expression). ... ATG and AUG denote sequences of DNA and RNA respectively that are the start codon or initiation codon encoding the amino acid methionine (Met) in eukaryotes and a modified Met (fMet) in prokaryotes. ...

Importance of rRNA

Ribosomal RNA characteristics are important in medicine and in evolution. For the chemical substances known as medicines, see medication. ... This article is about evolution in biology. ...

  • rRNA is the most conserved (least variable) gene in all cells. For this reason, genes that encode the rRNA (rDNA) are sequenced to identify an organism's taxonomic group, calculate related groups, and estimate rates of species divergence. For this reason many thousands of rRNA sequences are known and stored in specialized databases such as RDP-II[2] and the European SSU database.[3]

An antibiotic is a drug that kills or slows the growth of bacteria. ... Chloramphenicol is a bacteriostatic antibiotic originally derived from the bacterium Streptomyces venezuelae, isolated by David Gottlieb, and introduced into clinical practice in 1949. ... Erythromycin is a macrolide antibiotic which has an antimicrobial spectrum similar to or slightly wider than that of penicillin, and is often used for people who have an allergy to penicillins. ... Paromomycin sulfate (brand name Humatin) is a drug that fights intestinal amoeba infection, or amebiasis. ... Castor beans The protein ricin (pronounced ) is a toxin from the castor bean (Ricinus communis). ... Spectinomycin hydrochloride (Trobicin®) is an aminocyclitol antibiotic produced by the bacteria Streptomyces spectabilis. ... Streptomycin is an antibiotic drug, the first of a class of drugs called aminoglycosides to be discovered, and was the first antibiotic remedy for tuberculosis. ... Taxonomy (from Greek ταξινομία from the words taxis = order and nomos = law) may refer to either a hierarchical classification of things, or the principles underlying the classification. ...

Nucleolar dominance

Nucleolar dominance has also been shown for rRNA genes. In some organisms, particularly plants, when two nuclei are combined into a single cell during hybridization the developing organism can 'choose' one set of rRNA genes for transcription. The rRNA genes of the other parent are suppressed and not generally transcribed, though reactivation of the suppressed or 'inferior' rRNA genes may occasionally occur. This selective preference of transcription of rRNA genes is termed nucleolar dominance.

See also

Ribotyping involves the fingerprinting of genomic DNA restriction fragments that contain all or part of the genes coding for the 16S and 23S rRNA. Conceptually, ribotyping is similar to probing restriction fragments of chromosomal DNA with cloned probes (randomly cloned probes or probes derived from a specific coding sequence such...


  1. ^ Yusupov MM, Yusupova GZ, Baucom A, et al (2001). "Crystal structure of the ribosome at 5.5 A resolution". Science 292 (5518): 883-96. doi:10.1126/science.1060089. PMID 11283358. 
  2. ^ Cole, JR; Chai B, Marsh TL, Farris RJ, Wang Q, Kulam SA, Chandra S, McGarrell DM, Schmidt TM, Garrity GM, Tiedje JM (2003). "The Ribosomal Database Project (RDP-II): previewing a new autoaligner that allows regular updates and the new prokaryotic taxonomy". Nucleic Acids Res 31: 442–443. PMID 12520046. 
  3. ^ Wuyts, J; Van de Peer Y, Winkelmans T, De Wachter R (2002). "The European database on small subunit ribosomal RNA". Nucleic Acids Res 30: 183–185. PMID 11752288. 

A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ...

External links

Medical Subject Headings (MeSH) is a huge controlled vocabulary (or metadata system) for the purpose of indexing journal articles and books in the life sciences. ...

v  d  e
Major families of biochemicals
Peptides | Amino acids | Nucleic acids | Carbohydrates | Lipids | Terpenes | Carotenoids | Tetrapyrroles | Enzyme cofactors | Steroids | Flavonoids | Alkaloids | Polyketides | Glycosides
Analogues of nucleic acids: Types of Nucleic Acids Analogues of nucleic acids:
Nucleobases: Purine (Adenine, Guanine) | Pyrimidine (Uracil, Thymine, Cytosine)
Nucleosides: Adenosine/Deoxyadenosine | Guanosine/Deoxyguanosine | Uridine | Thymidine | Cytidine/Deoxycytidine
Nucleotides: monophosphates (AMP, UMP, GMP, CMP) | diphosphates (ADP, UDP, GDP, CDP) | triphosphates (ATP, UTP, GTP, CTP, GTPgammaS) | cyclic (cAMP, cGMP, cADPR)
Deoxynucleotides: monophosphates (dAMP, TMP, dGMP, dCMP) | diphosphates (dADP, TDP, dGDP, dCDP) | triphosphates (dATP, TTP, dGTP, dCTP)
Ribonucleic acids: RNA | mRNA | piRNA | tRNA | rRNA | ncRNA | gRNA | shRNA | siRNA | snRNA | miRNA | snoRNA
Deoxyribonucleic acids: DNA | mtDNA | cDNA | plasmid | Cosmid | BAC | YAC | HAC
Analogues of nucleic acids: GNA | PNA | TNA | Morpholino | LNA

  Results from FactBites:
Non-coding RNA - Wikipedia, the free encyclopedia (1015 words)
Ribosomal RNA (rRNA) is the primary constituent of ribosomes.
Ribosomes are the protein-manufacturing organelles of cells and exist in the cytoplasm and attached to the membrane of the endoplasmic reticulum.
Efference RNA ( eRNA) is derived from intron sequences of genes or from non-coding DNA.
Nucleolin functions in the first step of ribosomal RNA processing (8938 words)
Ribosome biogenesis is a complex process which involves the transcription of a large rRNA precursor, its maturation and assembly with ribosomal proteins ( Hadjiolov, 1985 ; Eichler and Craig, 1994).
A radiolabeled RNA corresponding to nucleotides +541 to +1250 of the mouse rRNA (RNA
RNA was extracted from the second half of the processing reaction used in Figure 2A and analyzed on a denaturing gel ( Figure 2B).
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