Abstract
Lipoteichoic acid is a major lipid-anchored polymer in Gram-positive bacteria such asBacillus subtilis. This polymer typically consists of repeating phosphate-containing units and therefore has a predominant negative charge. The repeating units are attached to a glycolipid anchor which has a diacylglycerol (DAG) moiety attached to a dihexopyranose head group. D-alanylation is known as the major modification of type I and type IV lipoteichoic acids, which partially neutralizes the polymer and plays important roles in bacterial survival and resistance to the host immune system. The biosynthesis pathways of the glycolipid anchor and lipoteichoic acid have been fully characterized. However, the exact mechanism of D-alanyl transfer from the cytosol to cell surface lipoteichoic acid remains unclear. Here I report the use of mass spectrometry in the identification of possible intermediate species in the biosynthesis and D-alanylation of lipoteichoic acid: the glycolipid anchor, nascent lipoteichoic acid primer with one phosphoglycerol unit, as well as mono- and di-alanylated forms of the lipoteichoic acid primer. Monitoring these species as well as the recently reported D-alanyl-phosphatidyl glycerol should aid in shedding light on the mechanism of the D-alanylation pathway of lipoteichoic acid.
Highlights
Phospholipids are the dominant cell membrane component in most bacteria[1] which render bacterial cell surface negatively charged
Aminoacylated lipids play an apparent role in surface charge modulation of Gram-positive bacteria[5]
The Bligh and Dyer method[24] carried out at an icy temperature appeared to be essential for successful extraction of species that are almost certainly lipoteichoic acid primer and its monoand di-alanylated derivatives
Summary
Phospholipids are the dominant cell membrane component in most bacteria[1] which render bacterial cell surface negatively charged. This feature makes bacterial membrane the easy target of host immune molecules such as cationic antibiotic peptides[2,3,4]. It should be specified that the author refers to type I LTA. The first part of the introduction is very simplified, for example no lipid A is mentioned, nor the modification it can suffer to make it less anionic. YL: I will redraw the molecular figures to make the two lines in double bonds in the same thickness and redraw the glucosyl rings in chair conformation
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