"We're interested in understanding how mutations in proteins can affect the way that cells communicate with each other," said Jeff Hasty, a professor of bioengineering at UC San Diego and senior author of the study, published November 10 in the journal Molecular Systems Biology. "This is important because it could help us understand how mutations contribute to disease, such as cancer, and how to develop new therapies to target those mutations."
In the study, Hasty and his team focused on a pair of proteins called LuxR and LuxI, which are involved in cell signaling in the bacterium Vibrio fischeri. V. fischeri is a bioluminescent bacterium that lives in the light organs of certain fish and squids. When V. fischeri cells are exposed to a certain chemical, LuxR and LuxI interact to activate a gene that produces luciferase, an enzyme that emits light.
The researchers used a technique called fluorescence resonance energy transfer (FRET) to measure the interaction between LuxR and LuxI. FRET is a process in which energy is transferred from one fluorescent molecule to another. The researchers attached one fluorescent molecule to LuxR and another to LuxI, and then used a microscope to measure the amount of energy transfer between the two molecules.
The researchers found that mutations in either LuxR or LuxI could affect the interaction between the two proteins, and that the strength of the interaction was correlated with the level of light production. This suggests that mutations that interfere with the interaction between LuxR and LuxI could make V. fischeri cells less responsive to the chemical signal that triggers light production.
The researchers also found that mutations in LuxR and LuxI could have different effects depending on the context in which they occurred. For example, a mutation that interfered with the interaction between LuxR and LuxI in one strain of V. fischeri did not have the same effect in another strain. This suggests that the effects of mutations can be context-dependent, and that it is important to consider the specific environment in which a mutation occurs when interpreting its effects.
"Our study provides a way to measure the effects of mutations on protein interactions in a quantitative way," said Hasty. "This information can help us understand how mutations contribute to disease and how to design new therapies to target those mutations."
In addition to Hasty, the study was also co-authored by UC San Diego graduate student Alexander Wong and postdoctoral researcher Michael Harrington. The study was supported by the National Institutes of Health.
