migA, a quorum-responsive gene of Pseudomonas aeruginosa, is highly expressed in the cystic fibrosis lung environment and modifies low-molecular-mass lipopolysaccharide

Yang, Hongjiang; Matewish, Mauricia J.; Loubens, Isabelle; Storey, Douglas G.; Lam, Joseph S.; Jin, Shouguang

doi:10.1099/00221287-146-10-2509

Cited by 28 publications

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“…2). Thus, migA upregulation by the quorum-sensing system may be the reason that P. aeruginosa clinical isolates from the lungs of cystic fibrosis patients express little or no O antigen (32). These results provide further evidence that MigA is a rhamnosyltransferase responsible for the ␣-1,6 linkage of L-Rha to the LPS core in P. aeruginosa.…”

Section: Discussionsupporting

confidence: 59%

“…Since expression of MigA from the pUCP26 complementation vector is constitutive, whereas the chromosomal migA gene is regulated by the RhlI/RhlR quorum-sensing regulatory system (32), the complemented cells contain a larger amount of expressed MigA than wild-type cells. Overexpression of MigA results in a reduction in the core-plus-one level in the cell (32), possibly because a larger amount of MigA outcompetes the activity of WapR to add L-Rha to nascent core OS, which is then committed to forming the uncapped core glycoform with an ␣-1,6-linked L-Rha. This explains the loss of reactivity with core-plusone-specific MAb 18-19, as the limited supply of capped core OS is processed to produce the high-molecular-weight LPS with O antigen observed (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…MigA and WapR share 54% similarity. Enhanced expression of migA was observed when P. aeruginosa wild-type strain PAO1 or PAK was grown in the presence of sputum from cystic fibrosis patients and was correlated with reduced production of lowmolecular-weight LPS (29,32). Interestingly, overexpression of MigA resulted in a reduction in the amount of capped core OS with one O-antigen repeat unit (called "core-plus-one") but not in the amount of A-band or B-band LPS, which contains capped core OS with many O-antigen repeat units.…”

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confidence: 99%

“…Also, P. aeruginosa isolated from clinical sputum samples invariably exhibited an increase in the expression of migA transcripts (32). Although migA is known to be regulated by the RhlI/ RhlR quorum-sensing regulatory system, the function of MigA has not been described yet (32). In this paper, we describe characterization of the putative rhamnosyltransferases WapR and MigA.…”

mentioning

confidence: 99%

“…Interestingly, overexpression of MigA resulted in a reduction in the amount of capped core OS with one O-antigen repeat unit (called "core-plus-one") but not in the amount of A-band or B-band LPS, which contains capped core OS with many O-antigen repeat units. Also, P. aeruginosa isolated from clinical sputum samples invariably exhibited an increase in the expression of migA transcripts (32). Although migA is known to be regulated by the RhlI/ RhlR quorum-sensing regulatory system, the function of MigA has not been described yet (32).…”

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Functional Characterization of MigA and WapR: Putative Rhamnosyltransferases Involved in Outer Core Oligosaccharide Biosynthesis ofPseudomonas aeruginosa

et al. 2008

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Pseudomonas aeruginosa lipopolysaccharide (LPS) contains two glycoforms of core oligosaccharide (OS); one form is capped with O antigen through an ␣-1,3-linked L-rhamnose (L-Rha), while the other is uncapped and contains an ␣-1,6-linked L-Rha. Two genes in strain PAO1, wapR (PA5000) and migA (PA0705), encode putative glycosyltransferases associated with core biosynthesis. We propose that WapR and MigA are the rhamnosyltransferases responsible for the two linkages of L-Rha to the core. Knockout mutants with mutations in both genes were generated. The wapR mutant produced LPS lacking O antigen, and addition of wapR in trans complemented this defect. The migA mutant produced LPS with a truncated outer core and showed no reactivity to outer core-specific monoclonal antibody (MAb) 5C101. Complementation of this mutant with migA restored reactivity of the LPS to MAb 5C101. Interestingly, LPS from the complemented migA strain was not reactive to MAb 18-19 (specific for the core-plus-one O repeat). This was due to overexpression of MigA in the complemented strain that caused an increase in the proportion of the uncapped core OS, thereby decreasing the amount of the core-plus-one O repeat, indicating that MigA has a regulatory role. The structures of LPS from both mutants were elucidated using nuclear magnetic resonance spectroscopy and mass spectrometry. The capped core of the wapR mutant was found to be truncated and lacked ␣-1,3-L-Rha. In contrast, uncapped core OS from the migA mutant lacked ␣-1,6-L-Rha. These results provide evidence that WapR is the ␣-1,3-rhamnosyltransferase, while MigA is the ␣-1,6-rhamnosyltransferase.Pseudomonas aeruginosa is an important gram-negative opportunistic pathogen capable of producing virulence determinants, including secreted toxins and enzymes, as well as cell surface structures, such as adhesins, flagella, and lipopolysaccharide (LPS) (18). LPS is a glycolipid composed of three distinct regions: lipid A, core oligosaccharide, and O antigen. P. aeruginosa produces two forms of O antigen, which are the homopolymeric A band and the heteropolymeric B band (15,21). The gene clusters associated with the biosynthesis of Aband and B-band O antigen in P. aeruginosa have been well characterized (for reviews, see references 18 and 22). In contrast, relatively little is known about the biosynthesis of the core oligosaccharide (OS).The P. aeruginosa core OS, like that of other gram-negative bacteria, can be conceptually subdivided into the inner core and the outer core (Fig. 1). The inner core is highly conserved and contains two L-glycero-D-manno-heptose (Hep) residues and two 3-deoxy-D-manno-octulosonic acid (Kdo) residues; the genetics and enzymology of this region are the best understood to date (14). The outer core is composed of four D-glucose (D-Glc) residues, one L-rhamnose (L-Rha) residue, and one N-(L-alanyl)-D-galactosamine residue, and its biosynthesis is not fully understood. The structures of the core OS of several different serotypes, clinical isolates, and rough mutants of P. a...

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Section: Discussionsupporting

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