Journal
MOLECULAR MICROBIOLOGY
Volume 67, Issue 2, Pages 264-277Publisher
BLACKWELL PUBLISHING
DOI: 10.1111/j.1365-2958.2007.06044.x
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Funding
- NIAID NIH HHS [R01 AI064184, R01-AI064184] Funding Source: Medline
- NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES [R01AI064184] Funding Source: NIH RePORTER
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One-third of the lipid A found in the Escherichia coli outer membrane contains an unsubstituted diphosphate unit at position 1 (lipid A 1-diphosphate). We now report an inner membrane enzyme, LpxT (YeiU), which specifically transfers a phosphate group to lipid A, forming the 1-diphosphate species. P-32-labelled lipid A obtained from IpxT mutants do not produce lipid A 1-diphosphate. In vitro assays with Kdo(2)-[4'-P-32]lipid A as the acceptor shows that LpxT uses undecaprenyl pyrophosphate as the substrate donor. Inhibition of lipid A 1-diphosphate formation in wild-type bacteria was demonstrated by sequestering undecaprenyl pyrophosphate with the cyclic polypeptide antibiotic bacitracin, providing evidence that undecaprenyl pyrophosphate serves as the donor substrate within whole bacteria. LpxT-catalysed phosphorylation is dependent upon transport of lipid A across the inner membrane by MsbA, a lipid A flippase, indicating a periplasmic active site. In conclusion, we demonstrate a novel pathway in the periplasmic modification of lipid A that is directly linked to the synthesis of undecaprenyl phosphate, an essential carrier lipid required for the synthesis of various bacterial polymers, such as peptidoglycan.
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