Characterization of the structure and catalytic activity of Legionella pneumophila VipF

The pathogenic bacteria Legionella pneumophila is known to cause Legionnaires' Disease, a severe pneumonia that can be fatal to immunocompromised individuals and the elderly. Shohdy et al. identified the L. pneumophila vacuole sorting inhibitory protein VipF as a putative N‐acetyltransferase based on sequence homology. We have characterized the basic structural and functional properties of VipF to confirm this original functional assignment. Sequence conservation analysis indicates two putative CoA‐binding regions within VipF. Homology modeling and small angle X‐ray scattering suggest a monomeric, dual‐domain structure joined by a flexible linker. Each domain contains the characteristic beta‐splay motif found in many acetyltransferases, suggesting that VipF may contain two active sites. Docking experiments suggest reasonable acetyl‐CoA binding locations within each beta‐splay motif. Broad substrate screening indicated that VipF is capable of acetylating chloramphenicol and both domains are catalytically active. Given that chloramphenicol is not known to be N‐acetylated, this is a surprising finding suggesting that VipF is capable of O‐acetyltransferase activity. Proteins 2016; 84:1422–1430. © 2016 Wiley Periodicals, Inc.