Effect of the PE Domain on the Activity of the Mycobacterium Tuberculosis Lipase, LipY (2015)

Undergraduates: Lindsey Broadwell, Brian Garrett

Faculty Advisor: Saskia Neher
Department: Chemistry

---

Mycobacterium tuberculosis is the causative agent of tuberculosis (TB), which resulted in 9 million new cases and 1.5 million deaths in 2013. Approximately 90% of newly infected individuals are asymptomatic due to the M. tuberculosis bacilli entering a dormant state. While dormant, M. tuberculosis accrues lipids from the host in the form of triglycerides (TAGs). In order to mobilize the TAGs for energy, lipases must break them down into free fatty acids. The only characterized M. tuberculosis TAG lipase, LipY, is part of the PE/PPE family of proteins named for a unique N-terminal domain with a proline glutamate or proline proline glutamate motif beginning at the ninth amino acid position. Although the function of PE/PPE proteins is not well defined, this protein family is specific to pathogenic mycobacterium and is assumed to contribute to the pathogen¿¿¿s virulence. Our lab recently demonstrated that purified LipY¿¿PE (without the PE domain) is more active than full length LipY. In order to specifically test the effect of the PE domain on the activity of LipY, we recombinantly expressed and purified LipY¿¿PE and the PE domain using nickel affinity- and size exclusion-chromatography. Next, we tested the activity of LipY¿¿PE incubated with different concentrations of the PE domain. Surprisingly we observed very little difference in lipase activity as a function of PE domain concentration. We concluded that the PE domain must be attached to LipY in order to regulate its activity.