Discovery of the Elusive UDP-Diacylglucosamine Hydrolase in the Lipid A Biosynthetic Pathway in Chlamydia trachomatis.
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Constitutive biosynthesis of lipid A via the Raetz pathway is essential for the viability and fitness of Gram-negative bacteria, includingChlamydia trachomatis Although nearly all of the enzymes in the lipid A biosynthetic pathway are highly conserved across Gram-negative bacteria, the cleavage of the pyrophosphate group of UDP-2,3-diacyl-GlcN (UDP-DAGn) to form lipid X is carried out by two unrelated enzymes: LpxH in beta- and gammaproteobacteria and LpxI in alphaproteobacteria. The intracellular pathogenC. trachomatislacks an ortholog for either of these two enzymes, and yet, it synthesizes lipid A and exhibits conservation of genes encoding other lipid A enzymes. Employing a complementation screen against aC. trachomatisgenomic library using a conditional-lethallpxHmutantEscherichia colistrain, we have identified an open reading frame (Ct461, renamedlpxG) encoding a previously uncharacterized enzyme that complements the UDP-DAGn hydrolase function inE. coliand catalyzes the conversion of UDP-DAGn to lipid Xin vitro LpxG shows little sequence similarity to either LpxH or LpxI, highlighting LpxG as the founding member of a third class of UDP-DAGn hydrolases. Overexpression of LpxG results in toxic accumulation of lipid X and profoundly reduces the infectivity ofC. trachomatis, validating LpxG as the long-sought-after UDP-DAGn pyrophosphatase in this prominent human pathogen. The complementation approach presented here overcomes the lack of suitable genetic tools forC. trachomatisand should be broadly applicable for the functional characterization of other essentialC. trachomatisgenes.IMPORTANCEChlamydia trachomatisis a leading cause of infectious blindness and sexually transmitted disease. Due to the lack of robust genetic tools, the functions of manyChlamydiagenes remain uncharacterized, including the essential gene encoding the UDP-DAGn pyrophosphatase activity for the biosynthesis of lipid A, the membrane anchor of lipooligosaccharide and the predominant lipid species of the outer leaflet of the bacterial outer membrane. We designed a complementation screen against theC. trachomatisgenomic library using a conditional-lethal mutant ofE. coliand identified the missing essential gene in the lipid A biosynthetic pathway, which we designatedlpxG We show that LpxG is a member of the calcineurin-like phosphatases and displays robust UDP-DAGn pyrophosphatase activityin vitro Overexpression of LpxG inC. trachomatisleads to the accumulation of the predicted lipid intermediate and reduces bacterial infectivity, validating thein vivofunction of LpxG and highlighting the importance of regulated lipid A biosynthesis inC. trachomatis.
Sequence Homology, Amino Acid
Published Version (Please cite this version)10.1128/mBio.00090-16
Publication InfoBarker, JR; Guan, Ziqiang; Valdivia, Raphael H; Young, HE; Zhao, J; & Zhou, Pei (2016). Discovery of the Elusive UDP-Diacylglucosamine Hydrolase in the Lipid A Biosynthetic Pathway in Chlamydia trachomatis. MBio, 7(2). pp. e00090. 10.1128/mBio.00090-16. Retrieved from http://hdl.handle.net/10161/11783.
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Research Professor in Biochemistry
We develop and apply mass spectrometry techniques to address biochemical and biomedical questions that are lipid-related. Research projects include: 1) Structural lipidomics o Develop and apply high resolution tandem mass spectrometry-based lipidomics for the discovery, structural elucidation and functional study of novel lipids. 2) Elucidation of novel pathways/enzymes of lipid biosynthesis and metabolism o Genetic, biochemical and MS a
Professor of Molecular Genetics and Microbiology
My laboratory is interested in how microbes influence human health, both in the context of host-pathogen and host-commensal interactions. For many pathogens, and certainly for most commensal microbes, the molecular basis of how host and microbial factors contribute to a beneficial outcome for us, is poorly understood. We currently focus on two experimental systems: Chlamydia trachomatis infections are responsible for the bulk of sexually transmitted ba
Professor of Biochemistry
Protein-protein interactions play a pivotal role in the regulation of various cellular processes. The formation of higher order protein complexes is frequently accompanied by extensive structural remodeling of the individual components, varying from domain re-orientation to induced folding of unstructured elements. Nuclear Magnetic Resonance (NMR) spectroscopy is a powerful tool for macromolecular structure determination in solution. It has the unique advantage of being capable of elucidati
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