Both prokaryotes and eukaryotes have ribosomes, but some antibiotics specifically target prokaryotic ribosomes. How is it possible to use these antibiotics to treat human diseases and how do they affect eukaryotic cells?
Antibiotics that target prokaryotic ribosomes can still be used to treat human diseases because although humans are eukaryotes, there are significant differences between prokaryotic and eukaryotic ribosomes. These differences allow certain antibiotics to selectively inhibit bacterial protein synthesis without affecting human cells.
Prokaryotes, such as bacteria, have 70S ribosomes composed of two subunits: the 30S small subunit and the 50S large subunit. In contrast, eukaryotes, including humans, have larger 80S ribosomes composed of a 40S small subunit and a 60S large subunit. This disparity in ribosome structure provides an opportunity for antibiotics to specifically target bacterial ribosomes.
One class of antibiotics that exploits this difference is the aminoglycosides, such as streptomycin and gentamicin. These antibiotics bind to the prokaryotic 30S subunit and interfere with the accurate reading of the mRNA codons during protein synthesis, leading to defective or non-functional bacterial proteins. Since eukaryotic ribosomes have a different structure, aminoglycosides have a significantly reduced effect on human cells.
Other antibiotics, like tetracyclines and macrolides, also target bacterial ribosomes, but by binding to different regions of the ribosome and interfering with specific steps of protein synthesis. Similarly, these antibiotics tend to have a lower impact on eukaryotic ribosomes due to the structural differences mentioned earlier.
However, it is important to note that there can still be some side effects of using antibiotics on human cells. Although these antibiotics have a higher selectivity for targeting bacterial ribosomes, some of them can still have adverse effects on human mitochondrial ribosomes, which are structurally similar to bacterial ribosomes. This can lead to unintended effects on mitochondrial protein synthesis and contribute to certain side effects seen with antibiotics.
In summary, antibiotics targeting prokaryotic ribosomes can be used to treat human diseases because of the structural differences between prokaryotic and eukaryotic ribosomes. They specifically interfere with bacterial protein synthesis while having a reduced impact on human cells. However, there can still be some potential side effects related to mitochondrial protein synthesis.