Domain organization of Legionella effector SetA

Area of Science:

• Microbiology
• Cell Biology
• Biochemistry

Background:

• Legionella pneumophila causes Legionnaires' disease pneumonia.
• Legionella effectors manipulate host cells for replication.
• The effector SetA shows similarity to glycosyltransferases and affects vesicular trafficking.

Purpose of the Study:

• To characterize the enzymatic activity and cellular localization of the Legionella effector SetA.
• To elucidate the functional domains of SetA responsible for its activity and targeting.
• To understand SetA's role in host-pathogen interactions.

Main Methods:

• Enzymatic assays using UDP-glucose as a substrate.
• Expression of EGFP-tagged SetA in HeLa cells and RAW 264.7 macrophages.
• Confocal microscopy to determine SetA localization.
• Yeast growth defect assays to assess functional domains.

Main Results:

• SetA exhibits glycohydrolase and mono-O-glucosyltransferase activity.
• The N-terminus contains catalytic activity, while the C-terminus directs SetA to vesicular compartments.
• SetA interacts with phosphatidylinositol 3-phosphate for localization to early endosomes and phagosomes.
• Both domains are essential for SetA's function, as shown by yeast growth defects.

Conclusions:

• SetA is a multidomain protein with distinct functional domains.
• The N-terminal domain possesses glucosyltransferase activity.
• The C-terminal domain binds phosphatidylinositol 3-phosphate, mediating localization to the Legionella-containing vacuole.
• Both localization and enzymatic activity are critical for SetA's cellular functions.