The effect of selenium enrichment on baker's yeast proteome

Abstract

The use of regular yeast (RY) and selenium-enriched yeast (SEY) as dietary supplement is of interest because the Nutritional Prevention of Cancer (NPC) trial revealed that SEY but not RY decreased the incidence of prostate cancer (PC). Using two-dimensional difference in gel electrophoresis (2D-DIGE)-tandem mass spectrometry (MS/MS) approach, we performed proteomic analysis of RY and SEY to identify proteins that are differentially expressed as a result of selenium enrichment. 2D-DIGE revealed 96 candidate protein spots that were differentially expressed (p≤0.05) between SEY and RY. The 96 spots were selected, sequenced by LC/MS/MS and 37 proteins were unequivocally identified. The 37 identified proteins were verified with ProteinProphet software and mapped to existing Gene Ontology categories. Furthermore, the expression profile of 5 of the proteins with validated or putative roles in the carcinogenesis process, and for which antibodies against human forms of the proteins are available commercially was verified by western analysis. This study provides evidence for the first time that SEY contains higher levels of Pyruvate Kinase, HSP70, and Elongation factor 2 and lower levels of Eukaryotic Translation Initiation Factor 5A-2 and Triosephosphate Isomerase than those found in RY.

Copyright © 2011 Elsevier B.V. All rights reserved.

Figures

Figure 1

Box plots demonstrating the spot intensity (expression values) distribution of the candidate proteins. The “red” plots show the distribution in SEY ranging from 0.55 to 1.54 and the blue plots show the distribution in RY ranging from 0.50 to 1.54;

Figure 2

2D-DIGE images for candidate protein spots 211 (A1, Pyruvate Kinase) up-regulated in SEY and 978 (B1, Eukaryotic Translation initiation Factor 5A-2; IF5A2) down-regulated in SEY. Images A2, B2 and A3, B3 are simulated 3-D and graphical representations of the spots illustrating differences in expression between SEY and RY.

Figure 3

ProteinProphet spectrum, scores and protein identity probability of one of the five peptides (KGDTYVSIQGFK) used for identification of Pyruvate Kinase (PK).

Figure 4

Western blot analysis of proteins expressed in selenium-enriched yeast (SEY) and regular yeast (RY). [A] Western blots of HSP70, Pyruvate Kinase (PK), Elongation Factor 2 (eEF2), Eukaryotic Translation Initiation Factor A-2 (eIF5A2) and Triosephosphate isomerase (TSP isomerase); [B] quantification of protein bond intensity (*, p