Structure Elucidation of Product of β-1,3-Glucosyltransferase Encoded by wfgD Gene in Escherichia Coli O152 Using Mass Spectrometry / 分析化学

ABSTRACT

The O152 antigens of Escherichia coli contains a Glc-β-1,3-GlcNAc linkage within the repeating unit. The wfgD gene in E. coli O152 O antigen gene cluster had been demonstrated utilizing NMR technique to encode a glucosyltransferase which is responsible for the synthesis of Glc-β-1,3-GlcNAc linkage. In this study, a synthetic substrate analog of the natural acceptor substrate undecaprenol-pyrophosphate-lipid [GlcNAc-α-PO_3-PO_3-(CH_2)_(11))-O-phenyl]) was used as an acceptor and UDP-Glc as a donor substrate, and electrospray ionization tandem mass spectrometry(ESI-MS-MS) was used for the detailed structural characte-)rization) of the enzyme product. A systematic study was conducted on product to allow rationalization of the fragmentation) processes. The major fragments observed in the ESI-MS-MS spectra result from cleavage of glycosidic) bond and diphosphate moiety. The fragment originating from the nonreducing end of the product yields information on sequence). Cross-ring cleavages, which are very informative of the linkages of the monosaccharide residues constituting) the product, and "internal" cleavage ions which are derived from elimination of substituents from around) the pyranose ring, were also observed. This extensive fragmentation was shown that the expected Glc-β-1,3-GlcNAc linkage in the product, confirming that wfgD is in the form of UDP-Glc: GlcNAc-pyrophosphate-lipid β-1,3-glucosyltransferase.)