Fatty acid insertion mechanism during membrane synthesis in Escherichia coli

Abstract:

[Objective] This study aimed to explore the mechanism of fatty acid insertion during membrane synthesis when cells grow and divide in Escherichia coli. [Methods] In the phosphatidylethanolamine (PE) synthesis pathway, acetyl-CoA was used as the substrate to synthesize long-chain acyl-ACP, followed by the synthesis of PE. The ten enzymes involved were each fused with a fluorescent protein such as enhanced green fluorescent protein (EGFP) or monmer Cherry (mCherry), and the fusion proteins were expressed in E. coli. The localizations of the fusion proteins were detected by laser scanning confocal fluorescence microscopy. [Results] Fluorescent microscope images showed that the proteins EGFP-FabA, EGFP-FabB, EGFP-FabI, EGFP-FabG, EGFP-PlsB, and EGFP-PssA accumulated in the polar and septal regions when expressed at high levels. Therefore, the ten enzymes displayed different localization patterns at different expression levels. Time-lapse imaging showed that EGFP-PlsB accumulated in the septum before cell division, then these regions of division became poles of the new cells. [Conclusion] This indicates that fatty acid inserted at the septum for PE synthesis and then PE was transported to all the other membrane regions.