PMID:2651435
| Citation |
Brozek, KA, Hosaka, K, Robertson, AD and Raetz, CR (1989) Biosynthesis of lipopolysaccharide in Escherichia coli. Cytoplasmic enzymes that attach 3-deoxy-D-manno-octulosonic acid to lipid A. J. Biol. Chem. 264:6956-66 |
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| Abstract |
Previous studies in our laboratory led to the elucidation of the covalent structure of a tetraacyldisaccharide 1,4'-bisphosphate precursor of lipid A (designated lipid IVA), that accumulates at 42 degrees C in temperature-sensitive mutants defective in 3-deoxy-D-manno-octulosonic acid (KDO) biosynthesis (Raetz, C. R. H., Purcell, S., Meyer, M. V., Qureshi, N., and Takayama, K. (1985) J. Biol. Chem. 260, 16080-16088). Using [4'-32P]lipid IVA as the probe, we now demonstrate the existence of cytoplasmic KDO-transferases in Escherichia coli capable of attaching 2 KDO residues, derived from CMP-KDO, to lipid IVA. A partial purification has been developed to obtain a cytoplasmic subfraction that adds these 2 KDO residues with a 90% yield. The product is shown to have the stoichiometry of (KDO)2-IVA by fast atom bombardment mass spectrometry and NMR spectroscopy. The partially purified enzyme can utilize alternative lipid-disaccharide cosubstrates bearing five or six fatty acyl chains, but it has an absolute requirement for a monophosphate residue at position 4' of the lipid acceptor. When reincubated with a crude cytoplasmic fraction, a nucleoside triphosphate and Mg2+, (KDO)2-IVA is rapidly metabolized to more polar substances, the identity of which is unknown. The KDO-transferase(s) described in the present study should be very useful for the semisynthetic preparation of complex lipopolysaccharide substructures and analogs. |
| Links | |
| Keywords |
Cytidine Triphosphate/pharmacology; Cytoplasm/enzymology; Escherichia coli/enzymology; Gas Chromatography-Mass Spectrometry; Lipid A/metabolism; Lipopolysaccharides/biosynthesis; Magnetic Resonance Spectroscopy; Substrate Specificity; Sugar Acids/metabolism; Time Factors; Transferases/metabolism |
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