What are 30S and 50S subunits?

Ribosomes are composed of two subunits with densities of 50S and 30S (“S” refers to a unit of density called the Svedberg unit). The 30S subunit contains 16S rRNA and 21 proteins; the 50S subunit contains 5S and 23S rRNA and 31 proteins. Ribosomal subunits are composed of ribosomal RNA (rRNA) and proteins.

What are 50S and 30S ribosomes?

The 50S subunit contains the 23S and 5S rRNA while the 30S subunit contains the 16S rRNA. Ribosome assembly consists of transcription, translation, the folding of rRNA and ribosomal proteins, the binding of ribosomal proteins, and the binding and release of the assembly components to make the ribosome.

What does the 50S ribosomal subunit do?

Function. 50S includes the activity that catalyzes peptide bond formation (peptidyl transfer reaction), prevents premature polypeptide hydrolysis, provides a binding site for the G-protein factors (assists initiation, elongation, and termination), and helps protein folding after synthesis.

Which ribozyme is associated with 50S subunit of ribosome?

rRNA
rRNA is a ribozyme which carries out protein synthesis in ribosomes. Ribosomal RNA is transcribed from ribosomal DNA (rDNA) and then bound to ribosomal proteins to form small and large ribosome subunits.

Why do 50S and 30S make 70S?

Protein synthesis begins with the interaction of the 30S subunit and mRNA through the Shine-Delgarno sequence. On formation of this complex, the initiator tRNA charged with formylmethionine binds to the initiator AUG codon, and the 50S subunit binds to the 30S subunit to form the complete 70S ribosome.

What is the S in 30S ribosome?

Bacteria and archaebacteria have smaller ribosomes, termed 70S ribosomes, which are composed of a small 30S subunit and large 50S subunit. The “S” stands for svedbergs, a unit used to measure how fast molecules move in a centrifuge.

Why 50S and 30S make 70S not 80S?

While the larger subunit sediments at 50S and the smaller at 30S together they sediment at 70S. Hence 50S+30S=70S and not 80S. The S is for Svedberg unit of sedimentation.

What do 30S ribosomes do?

The 30S ribosomal subunit has two primary functions in protein synthesis. It discriminates against aminoacyl transfer RNAs that do not match the codon of messenger RNA, thereby ensuring accuracy in translation of the genetic message in a process called decoding.

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