Doxycycline: Structure & Mechanism of Action

Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

This lesson is going to briefly describe doxycycline. Then you'll learn a bit about protein synthesis in order to understand exactly how doxycycline works its magic.

What is Doxycycline?

Have you heard of Vibramycin or Adoxa? Those are the trade names of something known as doxycycline, which is a really well-known antibiotic. An antibiotic is an agent that targets bacteria.

Doxycycline is a second generation antibiotic of the tetracycline class, a semisynthetic derivative of oxytetracycline, one that became available in 1967. It has better oral bioavailability and tissue penetration when compared to earlier kinds of tetracyclines.

You can spot its structure in this lesson as we go over its mechanism of action.

The 2D structure of doxycycline.
The 2D structure of doxycycline.

Protein Synthesis

Before we can fully appreciate how doxycycline works, we actually need to have a very simple but very important overview of how proteins are made.

Bacteria (and people for that matter) have what's known as ribosomes. The ribosome is the main site of protein synthesis. The ribosome itself is composed of a complex of protein and rRNA, or ribosomal RNA.

Each bacterial ribosome is composed of 2 subunits, two hamburger bun halves so to speak. In bacteria, the bigger bun is known as 50S, and the smaller bun is known as 30S.

When protein synthesis begins, these two hamburger bun halves assemble around a strand of mRNA, or messenger RNA. So, they kind of form a sandwich where mRNA is the 'meat' in the middle of the two hamburger buns.

This meat, or messenger RNA, encodes the way amino acids will assemble to form a protein. As protein synthesis continues, tRNA (transfer RNA) molecules attached to amino acids will lock into a corresponding sequence on the mRNA molecule.

Numerous tRNA molecules will dock in successive fashion to form a chain of amino acids that will jut out of the top of the ribosome. When the ribosome reaches a stop sequence on the mRNA molecule, it will detach itself from the mRNA and release the protein (amino acid chain) for the bacteria to use.

Without these proteins, bacteria cannot reproduce nor survive very well at all!

Mechanism of Action

So where does doxycycline play a part in all of this? Doxycycline's mechanism of action is via the inhibition of protein synthesis. It does so by interacting with the 30S subunit, the smaller hamburger bun half.

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