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Identification of new lipid metabolites in Escherichia coli total lipid extracts using electrospray ionization quadropole time of flight mass spectrometry
Author(s) -
Garrett Teresa A,
Raetz Christian R. H.
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a605-b
Subject(s) - chemistry , electrospray ionization , mass spectrometry , chromatography , lipid a , ion , phosphatidylserine , electrospray , biochemistry , phospholipid , organic chemistry , biology , bacteria , membrane , genetics
Using negative‐ion electrospray ionization time of flight mass spectrometry, we have begun systematically analyzing total lipid extracts of Escherichia coli in order to identify new lipid metabolites. Studies of DEAE fractionated lipids have led to the identification of several minor lipid species in the fractions which elute with high salt. Two enterobacterial common antigen related lipids, DGP‐disaccharide and ECA‐lipid III, were identified. In addition, we identified a series of ions [M–H] −1 with m/z of 861.48, 875.50, 887.50, 889.50, and 915.52 that did not correspond to known lipid structures. Collision‐induced decomposition (CID) of these lipid ions yields fragments corresponding to a glycerolphosphate based lipid with 2 acyl chains and a head group with a mass of 216 a.m.u. Fragment ions corresponding to loss of 44 a.m.u were also derived from these ions indicating the presence of a free carboxylic acid on the head group. We hypothesize that these ions correspond to phosphatidylserylglutamte in which a glutamate has been added via a peptide linkage to the carboxyl group of the serine head group of phosphatidylserine. Comparison of the CID spectrum of these ions to that of a semi‐synthetic standard (Avanti Polar Lipids) showed that all of the fragment ions derived from the serylglutamate headgroup were identical. Work now focuses on the development of an in vitro enzyme assay for the formation of phosphatidylserylglutamate and the identification of new lipid structures in the remaining DEAE fractions. This work was supported in part by the LIPID MAPS Large Scale Collaborative Grant number GM069338 from the NIH.