Molecular ruler mechanism and interfacial catalysis of the integral membrane acyltransferase PatA

[EN]Glycolipids are prominent components of bacterial membranes that play critical roles not only in maintaining the structural integrity of the cell but also in modulating host-pathogen interactions. PatA is an essential acyltransferase involved in the biosynthesis of phosphatidyl-myo-inositol mannosides (PIMs), key structural elements and virulence factors of Mycobacterium tuberculosis. We demonstrate by electron spin resonance spectroscopy and surface plasmon resonance that PatA is an integral membrane acyltransferase tightly anchored to anionic lipid bilayers, using a two-helix structural motif and electrostatic interactions. PatA dictates the acyl chain composition of the glycolipid by using an acyl chain selectivity "ruler." We established this by a combination of structural biology, enzymatic activity, and binding measurements on chemically synthesized nonhydrolyzable acyl- coenzyme A (CoA) derivatives. We propose an interfacial catalytic mechanism that allows PatA to acylate hydrophobic PIMs anchored in the inner membrane of mycobacteria, through the use of water-soluble acyl-CoA donors.This work was supported by the MINECO/FEDER EU contracts BFU201677427-C2-2-R, BFU2017-92223-EXP, PID2019-105649RB-I00, Severo Ochoa Excellence Accreditation SEV-2016-0644; the Basque Government contract KK-2019/00076; NIH R01AI149297 (to M.E.G.); the MINECO/FEDER EU contract BFU-2015-68981-P and the Basque Government (IT1264-19) (to F.-X.C.); MINECO/FEDER EU contract RTI2018-099592-B-C21 (to F.C.); the Canadian Glycomics Network Grant SD-1 (to T.L.L.). European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement no. 844905 (to B.T.); the Basque Government (to I.A.); CONACyT fellowship no. 291276 (to E.D.P.-P.)