Three phosphatidylglycerol-phosphate phosphatases in the inner membrane of Escherichia coli |
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Authors: | Lu Yi-Hsueh Guan Ziqiang Zhao Jinshi Raetz Christian R H |
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Institution: | Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710, USA. |
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Abstract: | The phospholipids of Escherichia coli consist mainly of phosphatidylethanolamine, phosphatidylglycerol (PG), and cardiolipin. PG makes up ~25% of the cellular phospholipid and is essential for growth in wild-type cells. PG is synthesized on the inner surface of the inner membrane from cytidine diphosphate-diacylglycerol and glycerol 3-phosphate, generating the precursor phosphatidylglycerol-phosphate (PGP). This compound is present at low levels (~0.1% of the total lipid). Dephosphorylation of PGP to PG is catalyzed by several PGP-phosphatases. The pgpA and pgpB genes, which encode structurally distinct PGP-phosphatases, were identified previously. Double deletion mutants lacking pgpA and pgpB are viable and still make PG, suggesting the presence of additional phosphatase(s). We have identified a third PGP-phosphatase gene (previously annotated as yfhB but renamed pgpC) using an expression cloning strategy. A mutant with deletions in all three phosphatase genes is not viable unless covered by a plasmid expressing either pgpA, pgpB, or pgpC. When the triple mutant is covered with the temperature-sensitive plasmid pMAK705 expressing any one of the three pgp genes, the cells grow at 30 but not 42 °C. As growth slows at 42 °C, PGP accumulates to high levels, and the PG content declines. PgpC orthologs are present in many other bacteria. |
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Keywords: | Bacterial Genetics Membrane Lipids Phosphatase Phosphatidylglycerol Phospholipid Metabolism Escherichia coli Mass Spectrometry PgpA PgpB PgpC |
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