What is rrna?

rRNA (Ribosomal RNA)

Ribosomal RNA, or rRNA, is a crucial component of ribosomes, the molecular machines responsible for protein synthesis in all living organisms. It's not merely a structural element; rRNA plays a catalytic role, meaning it helps speed up the chemical reactions involved in translation.

• Function: rRNA's primary role is to provide a structural framework for the ribosome and to catalyze the formation of peptide bonds between amino acids during protein synthesis.

• Structure: rRNA molecules are folded into complex three-dimensional structures, stabilized by interactions with ribosomal proteins. These structures form the ribosomal subunits: the large subunit and the small subunit. Different organisms have different sizes of rRNA molecules, commonly measured in Svedberg units (S). For example, in eukaryotic cells, the large subunit contains 28S, 5.8S, and 5S rRNA molecules, while the small subunit contains 18S rRNA. In prokaryotic cells, the large subunit contains 23S and 5S rRNA, and the small subunit contains 16S rRNA.

• Location: rRNA is synthesized in the nucleolus (in eukaryotes) and then assembled with ribosomal proteins in the cytoplasm to form functional ribosomes.

• Transcription and Processing: rRNA genes are transcribed by RNA polymerase I (in eukaryotes) as a single precursor molecule. This precursor is then processed and cleaved into the individual rRNA molecules.

• Evolutionary Significance: rRNA genes, particularly the 16S rRNA gene in prokaryotes and the 18S rRNA gene in eukaryotes, are highly conserved across different species. This makes them valuable tools for studying evolutionary relationships and for identifying different organisms in environmental samples. This is commonly used in phylogenetic analysis.

• Clinical Relevance: rRNA is a common target for antibiotics. Many antibiotics bind to bacterial rRNA, inhibiting protein synthesis and ultimately killing the bacteria. The differences between bacterial and eukaryotic rRNA allow for selective targeting of bacterial ribosomes without harming the host cells.