Characterization of the glucosyltransferase activity of Legionella pneumophila effector SetA
Legionella pneumophila glucosyltransferase SetA, which is introduced into target cells by a type IV secretion system, affects the intracellular traffic of host cells. Here, we characterized the enzyme activity of the Legionella effector. We report that Asp118 and Arg121 of SetA are essential for glucohydrolase and glucotransferase activities. Exchange of Trp36 to alanine reduced the enzyme activity of SetA. All three amino acids were crucial for the cytotoxic effects of SetA in yeast. We observed that phosphatidylinositol-3-phosphate (PI3P) increased the glucosyltransferase activity of SetA severalfold, while the glucohydrolase activity was not affected. In the presence of PI3P, we observed the glucosylation of actin, vimentin and the chaperonin CCT5 in the cytosolic fraction of target cells. Studies on the functional consequences of glucosylation of skeletal muscle α-actin in vitro revealed inhibition of actin polymerization by glucosylation.
KeywordsLegionella pneumophila effector SetA Glucosylation Enzyme activity Actin polymerization Vimentin CCT5
KA and TJ were responsible for the study concept, design and interpretation of data. NL, MS, KEB, SS and YB performed experiments and analysed data. AS was responsible for MS data. All authors critically reviewed and revised content and approved the final version for publication.
This study was financially supported by the Deutsche Forschungsgemeinschaft (project AK6/24-1).
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Conflict of interest
The authors declare that they have no competing interests.
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