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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

Esteve, Clara, Cañas, Benito, Moreno-Gordaliza, Estefanía, Río, Carmen del, García, María Concepción, Marina, María Luisa
Journal of agricultural and food chemistry 2011 v.59 no.22 pp. 12093-12101
Olea europaea, acyl carrier protein, chromatography, copper, databases, desorption, heat shock proteins, ionization, manganese, mass spectrometry, olive pulp, olives, polyacrylamide gel electrophoresis, zinc
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.