Biophysical Society Conference | Tahoe 2022

Molecular Biophysics of Membranes

Poster Abstracts

8-POS Board 2 THE LIPOPROTEIN LPRG TRANSPORTS AN UNKNOWN LIPID THAT IS REQUIRED FOR MYCOMEMBRANE IMPERMEABILITY IN THE PATHOGENIC MYCOBACTERIUM M. ABSCESSUS Nicholas Campbell-Kruger 1 ; Sarah Stanley 1,2 ; 1 University of California Berkeley, Molecular and Cell Biology, Berkeley, CA, USA 2 University of California Berkeley, School of Public Health, Berkeley, CA, USA Mycobacterium abscessus and other mycobacterial pathogens are characterized by the presence of an atypical outer membrane called the mycomembrane. The mycomembrane represents a formidable permeability barrier, giving M. abscessus high innate resistance to many classes of antibiotics. Historically, the impermeability of the mycomembrane has been attributed primarily to the α -branched, β -hydroxylated extremely long-chain fatty acids called mycolic acids that make up the inner leaflet and part of the outer leaflet of the mycomembrane. However, recent research has highlighted a variety of non-mycolic acid lipid species that contribute significantly to the impermeability of the mycomembrane. One such lipid species is the substrate of LprG, a lipoprotein, and its operonic partner, a Major Facilitator Superfamily transporter, both of which are widely conserved in mycobacteria. In M. tuberculosis and M. smegmatis, LprG has been shown to bind to and transport two components of the mycomembrane – triacylglycerides (TAGs) and phosphatidylinositol dimannosides (PIMs). However, the M. abscessus LprG aligns poorly with both the M. tuberculosis and the M. smegmatis LprG and structural models predict a significantly smaller binding pocket, suggesting that LprG transports different substrates in this species. To test the contribution of LprG to pathogenesis, antibiotic resistance, and lipid transport in M. abscessus we generated a mutant lacking the LprG-MFS operon. We found that the LprG- MFS deletion mutant is impaired in pathogenesis in a macrophage infection model and shows increased susceptibility to a wide range of antibiotics as assayed through minimum inhibitory concentration. However, we found through lipid extraction and thin layer chromatography that TAGs are more accessible to solvent extraction in the mutant, suggesting that LprG transports an as yet unidentified substrate to the mycomembrane in M. abscessus, or that the direction of LprG transport is retrograde rather than anterograde.

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