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LpxI structures reveal how a lipid A precursor is synthesized

Nature Structural & Molecular Biology volume 19, pages 1132–1138 (2012)Cite this article

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Abstract

Enzymes in lipid metabolism acquire and deliver hydrophobic substrates and products from within lipid bilayers. The structure at 2.55 Å of one isozyme of a constitutive enzyme in lipid A biosynthesis, LpxI from Caulobacter crescentus, has a novel fold. Two domains close around a completely sequestered substrate, UDP-2,3-diacylglucosamine, and open to release products either to the neighboring enzyme in a putative multienzyme complex or to the bilayer. Mutation analysis identifies Asp225 as key to Mg2+-catalyzed diphosphate hydrolysis. These structures provide snapshots of the enzymatic synthesis of a critical lipid A precursor.

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Figure 1: Lipid A is an essential membrane component of Gram-negative bacteria.
Figure 2: Topology and overall fold of CcLpxI and CcLpxI-D225A in complex with lipid X and UDP-2,3-diacylglucosamine, respectively.
Figure 3: Absolutely conserved polar residues mapped to the structure of CcLpxI-D225A.
Figure 4: Ligand binding in CcLpxI and CcLpxI-D225A.
Figure 5: CcLpxI dimerization.
Figure 6: A model for CcLpxI-mediated catalysis.

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Acknowledgements

We dedicate this paper to the memory of coauthor Christian R.H. Raetz (1946–2011), our dear colleague and friend. We thank H.S. Chung, D.A. Six, Z. Guan, G. Laird, J.M. Holton, N.I. Nicely, J.E. Pak and J.W. Werner-Allen for helpful discussions. We thank H.J. Sage for analytical ultracentrifugation services. This research was supported by the US National Institutes of Health grants U54GM094625 (to R.M.S.), GM24485 (to R.M.S.), GM51310 (to C.R.H.R.) and GM069338 (to C.R.H.R.).

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Author notes

  1. Christian R H Raetz: Deceased.

  2. Louis E Metzger and John K Lee: These authors contributed equally to this work.

Authors and Affiliations

  1. Department of Biochemistry and Biophysics, The University of California San Francisco, San Francisco, California, USA

    Louis E Metzger IV, John K Lee, Janet S Finer-Moore & Robert M Stroud

  2. Department of Biochemistry, Duke University, Durham, North Carolina, USA

    Christian R H Raetz

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Contributions

L.E.M. purified and biochemically characterized the protein. L.E.M. and J.K.L. determined and optimized the crystallization conditions, collected the crystallographic data and solved the structures. L.E.M., J.K.L. and J.S.F.-M. refined the structures. L.E.M., J.S.F.-M., C.R.H.R. and R.M.S. analyzed and interpreted the structures. L.E.M. performed and analyzed, with C.R.H.R., the LC/MS experiments. L.E.M. wrote the manuscript and J.S.F.-M. and R.M.S. edited the manuscript.

Corresponding authors

Correspondence to Louis E Metzger IV or Robert M Stroud.

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The authors declare no competing financial interests.

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Metzger, L., Lee, J., Finer-Moore, J. et al. LpxI structures reveal how a lipid A precursor is synthesized. Nat Struct Mol Biol 19, 1132–1138 (2012). https://doi.org/10.1038/nsmb.2393

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