Identification of phosphatidylserylglutamtate: A novel minor lipid in Escherichia coli

Teresa A. Garrett, Christian R. H. Raetz, Travis Richardson, Reza Kordestani, Jennifer D. Son, and Rebecca L. Rose

Chemistry, Vasssar College, Poughkeepsie, NY 12604

Corresponding Author: tegarrett{at}vassar.edu

Advances in mass spectrometry have facilitated the identification of novel lipid structures. In this work, we fractionated the lipids of E. coli B and analyzed the fractions using negative-ion electrospray ionization mass spectrometry in order to reveal unknown lipid structures. Analysis of a fraction eluting with high salt from DEAE cellulose revealed a series of ions not corresponding to any of the known lipids of E. coli. The ions, with m/z 861.5, 875.5, 887.5, 889.5, and 915.5, were analyzed using collision-induced decomposition mass spectrometry (MS/MS) and yielded related fragmentation patterns consistent with a novel diacylated glycerophospholipid. Product ions arising by neutral loss of 216 mass units were observed with all of the unknowns. A corresponding negative product ion was also observed at m/z 215.0. Additional ions at m/z 197.0, 171.0, 146.0, and 128.0 were used to propose the novel structure phosphatidylserylglutamate (PSE). The hypothesized structure was confirmed by comparison with the MS/MS spectrum of a synthetic standard. Normal phase LC-MS analysis further showed that the endogenous PSE and synthetic PSE eluted with the same retention times. PSE was also observed in the equivalent anion exchange fractions of total lipids extracted from the wild-type E. coli K-12 strain MG1655.

Add to CiteULike CiteULike Add to Complore Complore Add to Connotea Connotea Add to Del.icio.us Del.icio.us Add to Digg Digg Add to Reddit Reddit Add to Technorati Technorati What's this?