Slight Amino Acid Changes Lead to Substantial Differences in Enzyme Function

A team of researchers at the University of Queensland discovered that just a few changes to an enzyme’s amino acids can be enough to dramatically change its function, enabling microbes to inhabit greatly different environments. Their findings were published in the Journal of Biological Chemistry. 

The team came to this conclusion after investigating how Haemophilus influenzae bacteria colonize the human respiratory system. "This disease-causing bacterium is supremely adapted to living in humans, so much so that they cannot survive anywhere else," lead researcher Ulrike Kappler said.

"It turns out that one enzyme, MtsZ, is the key player in this adaptation. But, surprisingly, close relatives of this protein, which promotes Haemophilus survival exclusively inside humans, help other species of bacteria to survive exclusively in lakes,” he added. 

Their research shows that a sequence difference of just three amino acids, a difference of less than 0.25 per cent of the MtsZ enzyme sequence, changes the functionality of the enzyme between bacteria living in lakes compared with those living in humans. "In the natural world, tiny differences can lead to enormous functional changes—for example, humans and chimpanzees aren't exactly the same despite being 99 percent genetically similar," Kappler added.

"Now that we understand the unique structure of this enzyme in Haemophilus, we hope to develop ways to inhibit its specific function and remedy chronic respiratory conditions associated with this bacterium," Kappler concluded.