Elucidation of the 3-O-Deacylase Gene, pagL, Required for the Removal of Primary β-Hydroxy Fatty Acid from the Lipid A in the Nitrogen-fixing Endosymbiont Rhizobium etli CE3

Until now, the gene responsible for the 3-O-deacylation of lipid A among nitrogen-fixing endosymbionts has not been characterized. Several Gram-negative animal pathogens such as Salmonella enterica, Pseudomonas aeruginosa, and Bordetella bronchiseptica contain an outer membrane 3-O-deacylase (PagL)...

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Published in:	The Journal of biological chemistry Vol. 288; no. 17; pp. 12004 - 12013
Main Authors:	Brown, Dusty B., Muszyński, Artur, Salas, Omar, Speed, Kacie, Carlson, Russell W.
Format:	Journal Article
Language:	English
Published:	United States Elsevier Inc 26-04-2013 American Society for Biochemistry and Molecular Biology
Subjects:	Bacterial Proteins - genetics Bacterial Proteins - metabolism Carboxylic Ester Hydrolases - genetics Carboxylic Ester Hydrolases - metabolism Deacylase Fatty Acids - genetics Fatty Acids - metabolism Glycobiology and Extracellular Matrices Host Defense Host-Pathogen Interactions Hydrolases Lipid A Lipid A - biosynthesis Lipid A - genetics Lipopolysaccharide (LPS) Nitrogen Fixation PagL Phaseolus - microbiology Phaseolus - physiology Rhizobium - enzymology Rhizobium - genetics Rhizobium etli Symbiosis Symbiosis - physiology Host-Pathogen Interactions Symbiosis Deacylase PagL Rhizobium etli Hydrolases Host Defense Lipid A Lipopolysaccharide (LPS) Nitrogen Fixation
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Summary:	Until now, the gene responsible for the 3-O-deacylation of lipid A among nitrogen-fixing endosymbionts has not been characterized. Several Gram-negative animal pathogens such as Salmonella enterica, Pseudomonas aeruginosa, and Bordetella bronchiseptica contain an outer membrane 3-O-deacylase (PagL) that has been implicated in host immune evasion. The role of 3-O-deacylated lipid A among nitrogen-fixing endosymbionts, plant endophytes, and plant pathogens has not been studied. However, D'Haeze et al. (D'Haeze, W., Leoff, C., Freshour, G., Noel, K. D., and Carlson, R. W. (2007) J. Biol. Chem. 282, 17101–17113) reported that the lipopolysaccharide from Rhizobium etli CE3 bacteroids isolated from host bean root nodules contained exclusively tetraacylated lipid A that lacked a lipid A β-hydroxymyristyl residue, an observation that is consistent with the possibility of PagL activity being important in symbiosis. A putative pagL gene was identified in the R. etli genome sequence. With this information, we created a pagL− mutant strain derived from R. etli CE3. Using mass spectrometry, we demonstrated that the mutant lacks 3-O-deacylated lipid A. The parent and mutant LPS were very similar as determined by gel electrophoresis and glycosyl composition analysis using gas chromatography/mass spectrometry. However, fatty acid analysis showed that the mutant lipid A contained larger amounts of β-hydroxypentadecanoic acid than that of the parent. Furthermore, the mutant was adversely affected in establishing symbiosis with its host, Phaseolus vulgaris. Background:R. etli lipid-A de-O-acylation occurs during symbiosis. Results:R. etli produces PagL, which de-O-acylates lipid A, and is active on E. coli lipid A, and a pagL mutant has a symbiotic defect. Conclusion:R. etli CE3 contains PagL; PagL acts on diverse lipid A structures and may be needed for proper R. etli-bean symbiosis. Significance: PagL may be important for proper infection of the bean host plant.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 Submitted in partial fulfillment of the requirements for a Ph.D. degree at the University of Georgia.
ISSN:	0021-9258 1083-351X
DOI:	10.1074/jbc.M113.470484