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. 2019 Mar 7;15(3):e1007385. doi: 10.1371/journal.ppat.1007385

Fig 1. Model of phospholipid homeostasis systems in N. gonorrhoeae.

Fig 1

(A) In WT N. gonorrhoeae, MlaA, potentially interacting with an unknown partner, participates in retrograde trafficking of phospholipids from the outer leaflet of the outer membrane, through the periplasmic component of the system, MlaC, to the inner membrane MlaBDEF complex. The phospholipase PldA dimerizes to its active form upon detection of mis-localized phospholipids and removes the sn-1 and sn-2 fatty acid side chains. Different phospholipids are represented by lipid tails of different colors (phosphatidylglycerol [PG], yellow; phosphatidylcholine [PC], red; phosphatidylethanolamine [PE], blue). Native N. gonorrhoeae membrane phospholipid composition can be found in Table 4. (B) When MlaA is removed, phospholipids cannot be transported through the Mla system and invade the outer leaflet of the outer membrane. Increased amounts of membrane vesicles are also produced. (C) When the phospholipase PldA is overexpressed in the absence of MlaA, the PE substrate preference of PldA leads to a membrane phospholipid profile that is skewed toward PG, including in the outer leaflet of the outer membrane. OMV, outer membrane vesicle.