Identification of Olive (Olea europaea) Pulp Proteins by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry and Nano-Liquid Chromatography Tandem Mass Spectrometry
2011
Esteve, Clara | Cañas, Benito | Moreno-Gordaliza, Estefanía | Río, Carmen del | García, María Concepción | Marina, M. L.
Proteins in the pulp of olive (Olea europaea) constitute a minor fraction. They have been sparsely studied despite their suggested role in oil stability and olive allergenicity. The analysis of a pulp protein extract by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed a major band at 24 kDa that was subjected to tryptic in-gel digestion. Peptide extracts were analyzed by MALDI-TOF MS and nanoLC-MS/MS. The use of different search engines enabled the assignment of a number of fragmentation spectra to peptide sequences, identifying a major band as a thaumatin-like protein and other low-abundant proteins such a drought-induced protein SDi-6-like, an acyl carrier protein, Cu/Zn and Mn superoxide dismutases, a small heat shock protein, and an ATP-dependent protease subunit. Many of the produced spectra did not give good matches in the database searches, due to the scarce presence of O. europaea entries in protein databases. Nevertheless, a huge number of spectra corresponded to peptides, which showed a high degree of homology with others from sequenced organisms. These results proved that database searching with MS/MS spectra constitutes a promising approach for the characterization of olive pulp proteins.
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