Tetracycline

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Drug Name

Tetracycline is a natural antibiotic produced by strains of Streptomyces and is a member of the tetracycline class (Darken et al., 1960). The drug inhibits protein synthesis by binding to the small ribosomal subunit in susceptible bacteria, preventing them from accepting tRNAs in the A-site. Tetracycline is a broad-spectrum agent. It exhibits activity against gram-positive bacteria, gram-negative bacteria, and atypical organisms such as chlamydiae and protozoan parasites (Chopra and Roberts, 2001).

Table 1. Basic profile of tetracycline.

Description Broad-spectrum tetracycline antibiotic
Target(s) Ribosome (30S subunit)
Generic Tetracycline
Commercial Name Achromycin V, Actisite, Tetracycline Hydrochloride
Combination Drug(s) Bismuth subcitrate, metronidazole, lansoprazole
Other Synonyms N/A
IUPAC Name (4S,4aS,5aS,6S,12aR)-4-(dimethylamino)-1,6,10,11,12a-pentahydroxy-6-methyl-3,12-dioxo-4,4a,5,5a-tetrahydrotetracene-2-carboxamide
Ligand Code in PDB TAC
PDB Structure 1hnw (Structure of tetracycline bound to 30S ribosome).
ATC Classification J01AA07
RotateHydrogensLabels
Figure 1. 2D and 3D structures of Tetracycline (PDB ligand code: TAC).

Antibiotic Chemistry

The antibacterial properties of tetracycline can be attributed to its structural features. The drug is a flat fused-ring system containing hydrophilic functional groups (Figure 2). This enables it to make hydrophobic, stacking, and charged interactions with the ribosome (Brodersen et al., 2000).

Figure 2. Chemical structure of tetracycline. The rings are labeled in red. Structure created using ChemDraw.
Figure 2. Chemical structure of tetracycline. The rings are labeled in red. Structure created using ChemDraw.

Drug Information

Table 2. Chemical and physical properties (DrugBank).

Chemical Formula C22H24N2O8
Molecular Weight 444.4 g/mol
Calculated Predicted Partition Coefficient: cLogP -0.56
Calculated Predicted Aqueous Solubility: cLogS -2.5
Solubility (in water) 1.33 mg/mL
Predicted Topological Polar Surface Area (TPSA) 181.62 Å2

Drug Target

The ribosome is the macromolecular machine on which proteins are synthesized. It is targeted by many classes of antibiotics approved by the US FDA, including the tetracycline class. Tetracycline positions itself in the decoding center of the 30S ribosomal subunit and makes direct contact with rRNA. It inhibits the accommodation of tRNAs in the A-site following EF-Tu-dependent GTP hydrolysis and as a result, prevents polypeptide chains from forming.

Learn more about protein synthesis, and the ribosome.

Drug-Target Complex

Each ribosomal subunit is composed of protein chains and rRNA. X-ray crystallography of the Thermus thermophilus 30S subunit in complex with tetracycline (shown in Figure 3) revealed that the small subunit consists of (Arenz and Wilson, 2016) protein chains and the 16s rRNA (all colored in pink)

The primary binding site of tetracycline is within the decoding center in the 30S subunit. Its binding pocket, which is formed mostly by 16S rRNA, is about 7 Å deep and 20 Å wide. The fused-ring system of the drug makes hydrophobic interactions with the pocket, including with U1196 and a stacking interaction with C1054. The drug also forms hydrogen bonds with the 16S rRNA, notably with A965. The hydrophilic side of the drug also interacts with a magnesium ion which forms key salt bridges to phosphate oxygen atoms of G1197 and G1198 (Brodersen et al., 2000). The interactions between tetracycline and the 16S rRNA can be seen in Figure 3.

Figure 3. The left image shows the 50S ribosomal subunit. For clarity, the secondary binding site of tetracycline is not shown here. The inset shows the interactions made at the primary binding site. The drug is shown in gray, key 16S rRNA nucleotides are shown in pink, and a Mg2+ ion is shown in green. The hydrogen bond between the drug and A965 is shown in light blue, and interactions between the Mg2+ ion, the drug, and 16S rRNA are shown as purple dashed lines (PDB ID: 1hnw, Brodersen et al., 2000).
Figure 3. The left image shows the 50S ribosomal subunit. For clarity, the secondary binding site of tetracycline is not shown here. The inset shows the interactions made at the primary binding site. The drug is shown in gray, key 16S rRNA nucleotides are shown in pink, and a Mg2+ ion is shown in green. The hydrogen bond between the drug and A965 is shown in light blue, and interactions between the Mg2+ ion, the drug, and 16S rRNA are shown as purple dashed lines (PDB ID: 1hnw, Brodersen et al., 2000).

When tetracycline binds to the 30S subunit, it sterically blocks tRNAs from entering the A-site. As a result, if tRNAs do not bind to the codon of mRNAs, the polypeptide chain does not form (Arenz and Wilson, 2016). Superimposition of the structure of tRNA bound and tetracycline bound to the 70S ribosome can be seen in Figure 4 - the binding site of tetracycline overlaps the binding site of the tRNA anticodon in the A-site.

Figure 4. The structure of tetracycline bound to the 70S ribosomal subunit (PDB ID: 4v9a, Jenner et al., 2013) is superimposed with a structure of tRNAs bound to the 70S ribosome (PDB ID: 4v5d, Voorhees et al., 2009).
Figure 4. The structure of tetracycline bound to the 70S ribosomal subunit (PDB ID: 4v9a, Jenner et al., 2013) is superimposed with a structure of tRNAs bound to the 70S ribosome (PDB ID: 4v5d, Voorhees et al., 2009).

Multiple tetracycline binding sites have been discovered. In one study, crystals were soaked in 80 μM of tetracycline and the structure reported two tetracycline binding sites (Brodersen et al., 2000). In a second study, crystals were soaked in 4 μM of tetracycline and the structure revealed six tetracycline binding sites (Figure 5, Pioletti et al., 2001). However, only one site was common between the two studies—the site located in the decoding center. This location is termed the “primary binding site” and has the highest affinity for tetracycline (Nguyen et al., 2014).

Figure 5. The multiple binding sites of tetracycline. Tetracycline in the primary binding site is shown as gray spheres, and tetracycline molecules in their secondary binding sites are shown as yellow spheres (PDB ID: 1hnw, Brodersen et al., 2000), (PDB ID: 1i97, Pioletti et al., 2001).
Figure 5. The multiple binding sites of tetracycline. Tetracycline in the primary binding site is shown as gray spheres, and tetracycline molecules in their secondary binding sites are shown as yellow spheres (PDB ID: 1hnw, Brodersen et al., 2000), (PDB ID: 1i97, Pioletti et al., 2001).

Pharmacologic Properties and Safety

Table 3. Pharmacokinetics: ADMET of tetracycline.

Features Comment(s) Source
Oral Bioavailability (%) 60-80% orally while fasting, 100% intravenously, and less than 40% when administered via intramuscular injection DrugBank
IC50 6.50 μg/mL in E. coli (Grossman, 2016)
Ki (μM) N/A N/A
Half-Life (hrs) 6-12 hours DrugBank
Duration of Action N/A N/A
Absorption Site Occurs in the stomach and small intestine following oral administration (Chopra and Roberts, 2001)
Transporter(s) In gram-negative cells, it passively diffuses through outer membrane porins most likely as a Mg2+ chelator (Grossman, 2016)
Metabolism Not metabolized DrugBank
Excretion Excreted in the urine and feces at high concentration in a biologically active form DrugBank
AMES Test (Carcinogenic Effect) Probability 0.9132 (non-AMES toxic) DrugBank
hERG Safety Test (Cardiac Effect) Probability 0.9968 (weak inhibitor) DrugBank
Liver Toxicity High doses of tetracycline given intravenously can result in fatty liver disease, hepatic dysfunction, and acute liver failure LiverTox

Drug Interactions and Side Effects

Before starting treatment with tetracycline, patients should inform their healthcare provider if they have any of the following conditions:
1. Liver disease
2. Kidney disease
3. Allergies to any tetracycline antibiotics such as doxycycline or tigecycline

Tetracycline should not be given to children under 8 years old or pregnant women.

Table 4. Drug interactions and side effects of tetracycline.

Features Comment(s) Source
Total Number of Drug Interactions 162 drugs Drugs.com
Major Drug Interactions 12 drugs (ex: acitretin, mipomersen, vitamin A) Drugs.com
Alcohol/Food Interactions Coadministration of tetracycline with iron-containing or dairy products should be avoided since drug absorption is significantly decreased Drugs.com
Disease Interactions Colitis (major), Hepatotoxicity (moderate), Renal dysfunction (moderate), Esophageal irritation (moderate) Drugs.com
On-Target Side Effects Common tetracycline side effects include nausea, diarrhea, white patches/sores, and upset stomach, Drugs.com
Off-Target Side Effects N/A N/A
CYP Interactions Cytochrome P450 3A4 substrate DrugBank

Cases of Clostridium difficile associated diarrhea (CDAD) have been reported with the use of almost all antibacterial drugs, including tetracycline. This may vary in severity from mild diarrhea to fatal colitis. CDAD occurs because treatment with antibiotics changes the normal bacterial flora of the colon, which results in an overgrowth of C. difficile (FDA, 2017).

Regulatory Approvals/Commercial

Tetracycline was first patented in 1953 under the name Teracyn. Along with chlortetracycline and oxytetracycline, it is a first-generation member of the tetracycline class of antibiotics. Tetracycline is approved by the US FDA to treat a wide variety of infections, including those in the skin, soft tissue, lower respiratory tract, Rocky Mountain spotted fever, and infections caused by Chlamydia psittaci, Acne vulgaris, Escherichia coli, and Enterobacter aerogenes.

Links

Table 5: Links to learn more about tetracycline

Comprehensive Antibiotic Resistance Database (CARD) ARO: 0000051
DrugBank https://www.drugbank.ca/drugs/DB00759
Drugs.com https://www.drugs.com/tetracycline.html
FDA – Tetracycline Hydrochloride https://www.accessdata.fda.gov/drugsatfda_docs/label/2014/060704s035lbl.pdf
LiverTox: National Institutes of Health (NIH) https://www.ncbi.nlm.nih.gov/books/NBK547920/
PubChem CID 54675776

Learn about tetracycline resistance.

References

Arenz, S., Wilson, D. (2016). Bacterial protein synthesis as a target for antibiotic inhibition. Cold Spring Harbor Perspectives In Medicine, 6(9), a025361. https://doi.org/10.1101/cshperspect.a025361

Brodersen, D., Clemons, W., Carter, A., Morgan-Warren, R., Wimberly, B., Ramakrishnan, V. (2000). The structural basis for the action of the antibiotics tetracycline, pactamycin, and hygromycin B on the 30S ribosomal subunit. Cell, 103(7), 1143-1154. https://doi.org/10.1016/s0092-8674(00)00216-6 PDB ID: 1hnw

Chopra, I., Roberts, M. (2001). Tetracycline antibiotics: mode of action, applications, molecular biology, and epidemiology of bacterial resistance. Microbiology and molecular biology reviews : MMBR, 65(2), 232–260. https://doi.org/10.1128/mmbr.65.2.232-260.2001

Darken, M. A., Berenson, H., Shirk, R. J., Sjolander, N. O. (1960). Production of tetracycline by Streptomyces aureofaciens in synthetic media. Applied microbiology, 8(1), 46–51. https://doi.org/10.1128/am.8.1.46-51.1960

Grossman T. H. (2016). Tetracycline Antibiotics and Resistance. Cold Spring Harbor perspectives in medicine, 6(4), a025387. https://doi.org/10.1101/cshperspect.a025387

Jenner, L., Starosta, A. L., Terry, D. S., Mikolajka, A., Filonava, L., Yusupov, M., Blanchard, S. C., Wilson, D. N., Yusupova, G. (2013). Structural basis for potent inhibitory activity of the antibiotic tigecycline during protein synthesis. Proceedings of the National Academy of Sciences of the United States of America, 110(10), 3812–3816. https://doi.org/10.1073/pnas.1216691110 PDB ID: 4v9a

Jia, B., Raphenya, A. R., Alcock, B., Waglechner, N., Guo, P., Tsang, K. K., Lago, B. A., Dave, B. M., Pereira, S., Sharma, A. N., Doshi, S., Courtot, M., Lo, R., Williams, L. E., Frye, J. G., Elsayegh, T., Sardar, D. Westman, E. L., Pawlowski, A. C., Johnson, T. A., Brinkman, F. S., Wright, G. D., McArthur, A. G. (2017) CARD 2017: expansion and model-centric curation of the Comprehensive Antibiotic Resistance Database. Nucleic Acids Research 45, D566-573. https://doi.org/10.1093/nar/gkw1004

Nguyen, F., Starosta, A., Arenz, S., Sohmen, D., Dönhöfer, A., Wilson, D. (2014). Tetracycline antibiotics and resistance mechanisms. Biological Chemistry, 395(5). https://doi.org/10.1515/hsz-2013-0292

Pioletti, M., Schlünzen, F., Harms, J., Zarivach, R., Glühmann, M., Avila, H., Bashan, A., Bartels, H., Auerbach, T., Jacobi, C., Hartsch, T., Yonath, A., Franceschi, F. (2001). Crystal structures of complexes of the small ribosomal subunit with tetracycline, edeine and IF3. The EMBO journal, 20(8), 1829–1839. https://doi.org/10.1093/emboj/20.8.1829 PDB ID: 1i97

Tetracycline - DrugBank https://go.drugbank.com/drugs/DB00759

Tetracycline - Drugs.com https://www.drugs.com/tetracycline.html

Tetracycline Hydrochloride - FDA https://www.accessdata.fda.gov/drugsatfda_docs/label/2014/060704s035lbl.pdf

Tetracycline - PubChem https://pubchem.ncbi.nlm.nih.gov/compound/Tetracycline

Voorhees, R. M., Weixlbaumer, A., Loakes, D., Kelley, A. C., Ramakrishnan, V. (2009). Insights into substrate stabilization from snapshots of the peptidyl transferase center of the intact 70S ribosome. Nature structural & molecular biology, 16(5), 528–533. https://doi.org/10.1038/nsmb.1577 PDB ID: 4v5d

March 2025, Steven Arnold, Helen Gao, Shuchismita Dutta; Reviewed by Dr. Gerard Wright
https://doi.org/10.2210/rcsb_pdb/GH/AMR/drugs/antibiotics/prot-syn/ribo/TCY/tetracycline