Prokaryotic small ribosomal subunit

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30S
)
"30S" redirects here. For the decade AD 30–39, see
Sulfur-30
.
Atomic structure of the 30S Subunit from Thermus thermophilus. Proteins are shown in blue and the single RNA strand in orange.[1]

The prokaryotic small ribosomal subunit, or 30

70S prokaryotic ribosome
in prokaryotic cells. This 70S ribosome is then used to translate mRNA into proteins.

Function

The 30S subunit is an integral part of

prokaryotic initiation factors: IF-1, IF-2, and IF-3.[3]

A portion of the 30S subunit (the

f-Met-tRNA, binds and protein translation begins.[5] The binding site of the f-Met-tRNA on the 30S ribosomal subunit is called the "D-site"[6] This step is required in order for protein synthesis to occur. Then the large ribosomal subunit will bind and protein synthesis will continue.[7] The binding of the large subunit causes a conformational change in the 70S, which opens another site for protein translation.[6]

In order to form the translation complex with the 50S subunit, the 30S subunit must bind IF-1, IF-2, IF-3, mRNA, and f-met-tRNA. Next, the 50S subunit binds and a

initiation factors and resulting in protein translation.[8][5] This process is called "initiation" and is the slowest process of translation.[5]

Structure

The small ribosomal subunit is made up of 16S rRNA and 19 full proteins.

polypeptide chain that consists of 26 amino acids.[10] Conventionally, the rRNA is labeled with "H#" to indicate the helix number in high resolution images. Proteins are labelled "S#" to indicate the different peptides involved in rRNA stabilization. S11 and H45 are located near the Shine-Dalgarno binding site, which is also near the IF-3 binding site. Proteins S3, S4, S5, and S12, along with H18, are located near the channel where mRNA is present in the 30S subunit.[1]

Inhibition

The 30S subunit is the target of antibiotics such as tetracycline and gentamicin.[11] These antibiotics specifically target the prokaryotic ribosomes, hence their usefulness in treating bacterial infections in eukaryotes. Tetracycline interacts with H27 in the small subunit as well as binding to the A-site in the large subunit.[11] Puromycin is an inhibitor of ribosomal translation.[6] Pactamycin interrupts the binding in the Shine-Dalgarno binding region in the small subunit, thus disrupting activity. Hygromycin B also interacts with H44 and inhibits the translocation movement that is necessary during protein synthesis.[11]

See also

  • Prokaryotic large ribosomal subunit (50S)
  • Ribosomal RNA
  • Antibiotics

References

  1. ^
    PMID 11007480
    .
  2. S2CID 13069755
    .
  3. PMID 6170248
    .
  4. ^
    S2CID 17854788
    .
  5. ^
    PMID 2200518
    .
  6. ^
    PMID 4929429
    .
  7. PMID 4566460
    .
  8. PMID 20224578
    .
  9. PMID 7957245
    .
  10. PMID 8357533
    .
  11. ^
    PMID 11163189
    .

External links
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