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Understanding antibiotic resistance
Understanding antibiotic resistance

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2.2 Inhibitors of protein synthesis

You learned in Activity 1 that cells synthesise new proteins in ribosomes which are made up of one large and one small subunit. These subunits differ structurally and chemically between prokaryotic and eukaryotic ribosomes (Figure 5). This provides antibiotic targets in the bacterial pathogen which are not present in the host cells.

An image of the ribosome structure in prokaryotes (a) and eukaryotes (b).
Figure 5 Ribosome structure in (a) prokaryotes and (b) eukaryotes. The Svedberg unit (S) indicates the size, shape and density of each subunit.
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This figure shows the ribosome structure in prokaryotes (a) and eukaryotes (b). Part (a) shows the prokaryote 70S ribosome which is comprised of a large, 50S, and small, 30S, subunit represented as two blue ovals labelled 50S (top) and 30S (bottom). Part (b) shows the eukaryote 80S ribosome which is comprised of a large, 60S, and small, 40S, subunit represented as two blue ovals labelled 60S (top) and 40S (bottom). The large subunit of both ribosomes is responsible for creating the links in the growing amino acid chain. The small subunit in both ribosomes is where mRNA carrying the instructions for making protein binds. The Svedberg unit (S) indicates the size, shape and density of each subunit.

Figure 5 Ribosome structure in (a) prokaryotes and (b) eukaryotes. The Svedberg unit (S) indicates the size, shape and density of each ...
Table 1 Examples of protein synthesis inhibitor antibiotic classes
Ribosomal targetOutcomeAntibiotic classStructureExample drug
Small (30S) subunitErrors give rise to faulty proteins that disrupt the cell membraneAminoglycosidesAll contain amino sugar substructures (red)Streptomycin
Large (50S) subunitFirst steps of protein synthesis (initiation) are impaired and bacteria cannot grow and divideOxazolidinesAll contain 2-oxazolidone (red) somewhere in their structureLinezolid
(OpenStax College Microbiology, n.d.)