Identification of the Lyso-Form N -Acyl Intramolecular Transferase in Low-GC Firmicutes.

Autor:	Armbruster KM; Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, USA., Meredith TC; Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, USA txm50@psu.edu.
Jazyk:	angličtina
Zdroj:	Journal of bacteriology [J Bacteriol] 2017 May 09; Vol. 199 (11). Date of Electronic Publication: 2017 May 09 (Print Publication: 2017).
DOI:	10.1128/JB.00099-17
Abstrakt:	Bacterial lipoproteins are embedded in the cell membrane of both Gram-positive and Gram-negative bacteria, where they serve numerous functions central to cell envelope physiology. Lipoproteins are tethered to the membrane by an N -acyl- S -(mono/di)-acyl-glyceryl-cysteine anchor that is variously acylated depending on the genus. In several low-GC, Gram-positive firmicutes, a monoacyl-glyceryl-cysteine with an N-terminal fatty acid (known as the lyso form) has been reported, though how it is formed is unknown. Here, through an intergenic complementation rescue assay in Escherichia coli , we report the identification of a common orthologous transmembrane protein in both Enterococcus faecalis and Bacillus cereus that is capable of forming lyso-form lipoproteins. When deleted from the native host, lipoproteins remain diacylated with a free N terminus, as maturation to the N -acylated lyso form is abolished. Evidence is presented suggesting that the previously unknown gene product functions through a novel intramolecular transacylation mechanism, transferring a fatty acid from the diacylglycerol moiety to the α-amino group of the lipidated cysteine. As such, the discovered gene has been named l ipoprotein i ntramolecular t ransacylase ( lit ), to differentiate it from the gene for the intermolecular N -acyltransferase ( lnt ) involved in triacyl lipoprotein biosynthesis in Gram-negative organisms. IMPORTANCE This study identifies a new enzyme, conserved among low-GC, Gram-positive bacteria, that is involved in bacterial lipoprotein biosynthesis and synthesizes lyso-form lipoproteins. Its discovery is an essential first step in determining the physiological role of N-terminal lipoprotein acylation in Gram-positive bacteria and how these modifications impact bacterial cell envelope function. (Copyright © 2017 American Society for Microbiology.)
Databáze:	MEDLINE
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