Simone Lawson
Ribosomes are an essential cellular machine that performs protein biosynthesis. They are composed of ribosomal RNA (rRNA) and proteins. Bacterial ribosomes have two subunits, a small subunit (30S) and a large subunit (50S), that come together to form a complete 70S ribosome. The structure and composition of ribosomes are highly conserved in all species, however, some bacteria have been found to have an incomplete set of ribosomal proteins. The differences in the structure of bacterial ribosomes compared to eukaryotic ribosomes allow antibiotics to target and inhibit bacterial ribosomes while leaving human ribosomes unaffected.
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What You'll Learn
Bacterial ribosomes are composed of two subunits
The ribosome is a cytoplasmic nucleoprotein particle, and its main function is to serve as the site of mRNA translation and protein synthesis. The ribosome has a mass of about 2.5 MDa, with RNA accounting for 2/3 of the mass. The two subunits are composed of different molecules of ribosomal RNA (rRNA) and proteins. The 30S subunit contains 16S rRNA and 21 proteins, while the 50S subunit contains 5S and 23S rRNA and 31 proteins.
The density of the ribosome is measured in Svedberg (S) units, which correspond to the relative rate of sedimentation during ultra-high-speed centrifugation. The greater the S-value, the denser the particle. The ribosome's two subunits have different S-values due to their different compositions of rRNA and proteins.
The structure and composition of ribosomes are highly conserved in all species, although some bacteria have been found to have incomplete sets of ribosomal proteins. The protein composition of the large subunit is also less conserved than that of the small subunit.
The differences in the structure of bacterial ribosomes compared to those of eukaryotes allow for the development of antibiotics that can kill bacteria without affecting human cells. These antibiotics target the bacterial ribosomes, exploiting the structural differences to selectively inhibit their function and disrupt protein synthesis.
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The two subunits are 30S and 50S
The bacterial ribosome is a complex molecular machine that plays a crucial role in protein synthesis within the bacterium. It is composed of two subunits, denoted as 30S and 50S, which come together to form a functional 70S ribosome. These subunits differ in size, with the 30S subunit being smaller and the 50S subunit being larger.
The 30S subunit, also known as the small subunit, contains 16S ribosomal RNA (rRNA) and approximately 21 proteins. It plays a vital role in the initiation of translation by interacting with the messenger RNA (mRNA) and ensuring the correct start codon is selected. This subunit is crucial for the accurate reading of the genetic instructions necessary for protein synthesis.
The 50S subunit, on the other hand, is the larger subunit and contains both 5S and 23S rRNA molecules, as well as approximately 31 proteins. Together, these components contribute to the complex structure and functionality of the ribosome. The 50S subunit is involved in the binding of transfer RNA (tRNA) and the assembly of amino acids during protein synthesis.
The two subunits, 30S and 50S, work in harmony to facilitate the translation of mRNA into proteins. During this process, the subunits attach to the mRNA molecule, and the tRNA molecules bring the correct amino acids to the ribosome, inserting them according to the mRNA instructions. This process, known as translation, results in the formation of polypeptides and proteins that are essential for the bacterium's survival and function.
The unique structure and composition of bacterial ribosomes, particularly the 30S and 50S subunits, have been extensively studied using advanced techniques such as cryogenic electron microscopy (cryo-EM) and X-ray crystallography. These methods have provided valuable insights into the three-dimensional shape and chemical interactions of the ribosome, enabling the development of antibiotics that specifically target bacterial ribosomes while leaving human ribosomes unaffected.
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The two subunits come together to translate mRNA into proteins
The bacterial ribosome is a complex molecular machine found in the cytoplasm of prokaryotic cells, with a primary function of facilitating mRNA translation and protein synthesis. It is composed of two subunits, denoted as the 30S (small) and 50S (large) subunits, which come together to form a functional 70S ribosome. This process involves the ribosomal subunits attaching to the mRNA molecule, with the ribosome reading the codons and inserting the correct amino acids to create a polypeptide or protein chain.
The 30S subunit contains 16S rRNA and 21 proteins, while the 50S subunit consists of 5S and 23S rRNA, as well as 31 proteins. These subunits have different S-values, which correspond to their density and are measured in Svedberg units. The larger the S-value, the denser the particle. During translation, the ribosome moves along the mRNA molecule, adding amino acids according to the codons on the mRNA. This process is known as translation, where specific tRNA molecules bring the required amino acids to the ribosome and insert them in the correct order as dictated by the mRNA sequence.
The bacterial ribosome is an essential component of protein synthesis and has been extensively studied using techniques such as cryogenic electron microscopy (cryo-EM) and X-ray crystallography. These methods have helped elucidate the structure and function of ribosomes, allowing scientists to develop new antibiotics that can target bacterial ribosomes without affecting those in human cells.
The structure and composition of ribosomes are highly conserved across species, although some variations exist between bacterial, archaeal, and eukaryotic ribosomes. For instance, eukaryotic ribosomes are typically larger than bacterial ones and exhibit functional differences. Additionally, mitochondrial ribosomes in eukaryotic cells resemble bacterial ribosomes, reflecting the evolutionary origin of mitochondria as endosymbiotic bacteria.
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The ribosome has a mass of about 2.5 MDa
The bacterial ribosome is a nucleoprotein particle that performs mRNA translation and protein synthesis. It has a mass of about 2.5 MDa, with RNA accounting for 2/3 of the mass. The bacterial ribosome consists of two subunits, a small subunit (30S) and a large subunit (50S). When joined, the ribosome has a sedimentation coefficient of 70S. The small subunit contains 16S rRNA and 21 proteins, while the large subunit contains 5S, 23S rRNA, and 31 proteins.
The mass of the ribosome is an important factor in understanding its function and structure. With a mass of 2.5 MDa, the bacterial ribosome is relatively small compared to other cellular structures. This small size allows the ribosome to move freely within the cell and perform its function of mRNA translation and protein synthesis.
The mass of the ribosome is also related to its density. The ribosome has a density of 70S, which is a measure of its rate of sedimentation in centrifugation. The 70S ribosome is less dense than the 80S ribosome found in eukaryotes. The density of the ribosome is determined by the number and arrangement of its subunits.
The two subunits of the bacterial ribosome, 30S and 50S, have different densities and compositions. The 30S subunit is less dense than the 50S subunit and contains 16S rRNA and 21 proteins. The 50S subunit is denser and contains 5S and 23S rRNA, as well as 31 proteins. The arrangement of these subunits determines the overall density and structure of the ribosome.
The mass and density of the ribosome are important factors in the development of antibiotics. The differences in the structure of bacterial and eukaryotic ribosomes are exploited by pharmaceutical chemists to create antibiotics that can target bacterial infections without harming human cells. The bacterial 70S ribosome is vulnerable to certain antibiotics due to its unique structure, while the eukaryotic 80S ribosome is often unaffected.
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Bacterial ribosomes are vulnerable to antibiotics
Ribosomes are biological machines composed of RNAs and proteins that are responsible for protein synthesis. They are made up of two subunits that come together to translate messenger RNA (mRNA) into polypeptides and proteins during translation. Bacterial ribosomes are composed of three RNA chains (16S, 23S, and 5S) and more than 50 proteins assembled into two individual subunits, the small 30S and the large 50S subunits, which join together to form the 70S ribosome.
For example, the antibiotic chloramphenicol inhibits translation in a wide range of gram-positive and gram-negative bacteria, as well as in mitochondria, but not in the cytoplasm of eukaryotic cells. It binds to the A-site crevice of the 50S subunit, preventing the amino acid side chains of incoming aa-tRNAs from binding to the ribosome. Tetracyclines, another group of antibiotics, occupy the A-site of the bacterial 30S ribosomal subunit and inhibit bacterial polypeptide synthesis by blocking the recruitment of the aminoacyl-tRNA to the bacterial ribosome.
While antibiotics are intended to specifically target bacteria, some can also affect host cell physiology. For instance, aminoglycosides, a group of antibiotics, can induce the misreading and premature termination of mRNA translation in bacterial ribosomes, but they have also been associated with mitochondrial ribosomal dysfunction and side effects such as kidney injury and ototoxicity.
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Frequently asked questions
A bacterial ribosome is a cytoplasmic nucleoprotein particle that serves as the site of mRNA translation and protein synthesis.
Bacterial ribosomes consist of two subunits, a small subunit (30S) and a large subunit (50S), which combine to form a 70S ribosome. These subunits are composed of ribosomal RNA (rRNA) and proteins.
Bacterial ribosomes differ in size, sequence, structure, and the ratio of protein to RNA when compared to ribosomes from archaea and eukaryotes. These differences allow antibiotics to target bacterial ribosomes specifically, leaving human ribosomes unaffected.
Bacterial ribosomes are responsible for protein synthesis. They translate messenger RNA (mRNA) into polypeptides and proteins during translation.
