A Novel Lysophosphatidic Acid Acyltransferase of Escherichia coli Produces Membrane Phospholipids with a cis-vaccenoyl Group and Is Related to Flagellar Formation

Abstract

Lysophosphatidic acid acyltransferase (LPAAT) introduces fatty acyl groups into the sn-2 position of membrane phospholipids (PLs). Various bacteria produce multiple LPAATs, whereas it is believed that Escherichia coli produces only one essential LPAAT homolog, PlsC—the deletion of which is lethal. However, we found that E. coli possesses another LPAAT homolog named YihG. Here, we show that overexpression of YihG in E. coli carrying a temperature-sensitive mutation in plsC allowed its growth at non-permissive temperatures. Analysis of the fatty acyl composition of PLs from the yihG-deletion mutant (∆yihG) revealed that endogenous YihG introduces the cis-vaccenoyl group into the sn-2 position of PLs. Loss of YihG did not affect cell growth or morphology, but ∆yihG cells swam well in liquid medium in contrast to wild-type cells. Immunoblot analysis showed that FliC was highly expressed in ∆yihG cells, and this phenotype was suppressed by expression of recombinant YihG in ∆yihG cells. Transmission electron microscopy confirmed that the flagellar structure was observed only in ∆yihG cells. These results suggest that YihG has specific functions related to flagellar formation through modulation of the fatty acyl composition of membrane PLs.

Division of the role and physiological impact of multiple lysophosphatidic acid acyltransferase paralogs

“…S1). This is different from the phenotype of the E. coli yihG mutant, which is more motile than the wildtype cell and displays elevated flagellar expression [12]. E. coli YihG differs from PlsC4/PlsC5 in its substrate selectivity towards 18:1 [12].…”

“…The function of the putative acyltransferase YihG in E. coli remained unknown for a long time. However, we recently found it to be a putative ortholog of PlsC4 (39% identical) and demonstrated it as a novel LPAAT with a substrate specificity different from that of PlsC from E. coli [12]. As a BLAST search indicated that other bacteria such as Pseudomonas and Vibrio also have putative PlsC4/YihG ortholog(s), we expanded the scope of an ortholog search using the KEGG Ortholog Cluster database.…”

“…In addition, although Escherichia coli was considered to have one LPAAT encoded by plsC because its deletion is lethal [11], we recently demonstrated that yihG from E. coli codes for a second LPAAT and can substitute for plsC when it is overexpressed (therefore, we consider that it is reasonable to regard PlsC as a "principal" LPAAT, not the only LPAAT) [12]. YihG is a distant homolog of PlsC, with only 18% amino acid sequence identity, and shares several motifs of the PL acyltransferase.…”

Recent Advances in the Bacterial Flagellar Motor Study

“…The scope of this Special Issue is to cover recent advances in our understanding of the structures and functions of the bacterial flagellar motor derived from different bacterial species. This Special Issue includes ten review articles [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ] and eleven original research papers [ 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ] from well-known experts in the field.…”

“…E. coli has another LPAAT homolog named YihG in addition to PlsC, which is essential for the growth of E. coli . Toyotake et al constructed a yihG null mutant (∆ yihG ) and provided evidence suggesting that YihG has specific functions related to flagellar assembly through the modulation of the fatty acyl composition of membrane phospholipids [ 24 ].…”