Affiliation:
1. Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, USA
Abstract
ABSTRACT
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.
Funder
Eberly College of Sciences
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
28 articles.
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