Fig. 2
The 2-acyl-GPE cycle. The 2-acyl-GPE cycle initiates at the periplasmic side of the inner membrane with the conversion of PtdEtn into 2-acyl-GPE by the apolipoprotein N-acyltransferase Lnt which transfers the fatty acid moiety from the sn-1 position of phosphatidylethanolamine (PtdEtn) to the N terminus of the major outer membrane lipoprotein (Lpp). The 2-acyl-GPE is then transported to the cytoplasm through LplT protein. Once inside, the PtdEtn molecule is regenerated by the action of the 2-acyl-GPE acyltransferase/acyl-ACP synthethase Aas protein by the re-acylation of the 2-acyl-GPE molecule. Then the PtdEtn molecule is exported through the MsbA protein to the periplasmic side of the inner membrane. The abbreviations are as follows: phosphatidylethanolamine (PtdEtn), 2-acyl-glycerophosphatidylethanolamine (2-acyl-GPE), fatty acid (FA), Lipoprotein (Lpp), acylated lipoprotein (Acyl-Lpp), Apolipoprotein N-acyltransferase (Lnt), phospholipase A type 2 (PLA2), lipopolysaccharide transporter (MsbA), lysophospholipid transporter (LplT), 1-acylglycerol-3-phosphate O-acyltransferase (PlsC), 2-acylglycerophosphoethanolamine acyltransferase/acyl-ACP synthetase (Aas), acyl-ACP synthetase activity (ACP), 2-acylglycerophosphoethanolamine acyltransferase activity (ACS), Adenosine triphosphate (ATP), Adenosine monophosphate (AMP), inorganic pyrophosphate (PPi)