50S large subunit

Definition

The 50S large subunit is one of the two components of prokaryotic ribosomes, playing a vital role in protein synthesis. It consists of rRNA and proteins that work together to facilitate the translation process by ensuring that amino acids are assembled into polypeptides in the correct order according to mRNA sequences. This subunit interacts with the small 30S subunit to form a functional ribosome that translates mRNA into proteins, making it essential for cellular function and growth.

5 Must Know Facts For Your Next Test

1. The 50S large subunit contains two key rRNA molecules, 5S rRNA and 23S rRNA, which play crucial roles in the structure and function of the ribosome.
2. It interacts with the small 30S subunit during translation initiation, allowing for the proper alignment of mRNA and transfer RNA (tRNA).
3. The large subunit catalyzes the formation of peptide bonds between amino acids, which links them together to form a protein chain.
4. In prokaryotes, the entire ribosome has a sedimentation coefficient of 70S, with the 50S and 30S subunits contributing to this overall size.
5. Certain antibiotics target the 50S large subunit to inhibit protein synthesis in bacteria, showcasing its importance in bacterial metabolism.

Review Questions

• How does the 50S large subunit interact with the small subunit during protein synthesis?
  • The 50S large subunit interacts with the small 30S subunit to form a functional ribosome complex that is essential for protein synthesis. During initiation, the small subunit first binds to the mRNA strand and positions itself correctly. Then, the large subunit joins this complex, allowing for tRNA molecules to enter the A site and facilitating peptide bond formation through its enzymatic activity.
• Discuss the role of ribosomal RNA within the structure of the 50S large subunit and its importance in protein synthesis.
  • Ribosomal RNA (rRNA) within the 50S large subunit provides structural integrity and catalyzes biochemical reactions necessary for protein synthesis. The 5S rRNA and 23S rRNA work together to stabilize interactions between tRNA and mRNA while facilitating the formation of peptide bonds between amino acids. This highlights the dual role of rRNA as both a structural component and an enzymatic catalyst in translation.
• Evaluate how targeting the 50S large subunit with antibiotics affects bacterial growth and survival.
  • Targeting the 50S large subunit with antibiotics such as erythromycin or chloramphenicol inhibits protein synthesis in bacteria by blocking peptide bond formation or preventing tRNA binding. This disrupts critical cellular functions, leading to bacterial growth inhibition or death. The selective toxicity towards bacterial ribosomes (which differ from eukaryotic ribosomes) allows these antibiotics to effectively eliminate infections without harming human cells, illustrating their therapeutic importance.

Related terms

Ribosomal RNA (rRNA): A type of RNA that, together with proteins, makes up the structure of ribosomes and is crucial for their function in protein synthesis.

Translation: The process by which ribosomes synthesize proteins from messenger RNA (mRNA) templates, involving decoding the sequence of nucleotides into a chain of amino acids.

Small subunit (30S): The smaller component of prokaryotic ribosomes that binds to mRNA and initiates translation by providing a platform for the assembly of amino acids.