SUMMARY: Colistin is an antibiotic that is considered to be a last resort against antibiotic resistant bacteria. Unfortunately, an enzyme called MCR-4 has evolved which makes bacteria resistant to colistin. Researchers want to understand the structure and function of MCR-4 in order to combat it. There is a family of genes called mcr; they code for the enzymes MCR-1, MCR-2, MCR-3, and MCR-4. Researchers compared the different parts of the enzymes to figure out differences between each enzyme. MCR-4 works by preventing colistin from destroying the lipopolysaccharide cell wall of gram negative bacteria; this in turn prevents colistin from producing large amounts of reactive oxygen species in the bacteria.
LESSON COMMENTS: When teaching students about cell biology and biological processes, I often stress the importance of understanding structure and function, as well as being able to relate the two. This article would be best used in a biology class during a lesson on enzyme specificity or protein structure. The details in the Results section is a good example of how even small changes in amino acids can disable an enzyme.
Zhang, H., Hou, M., Xu, Y., Srinivas, S., Huang, M., Liu, L., & Feng, Y. (2019). Action and mechanism of the colistin resistance enzyme MCR-4. Communications biology, 2, 36. doi:10.1038/s42003-018-0278-1