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J Proteome Res. 2007 Sep;6(9):3465-74. Epub 2007 Aug 11.

Exploring novel function of yeast Ssa1/2p by quantitative profiling proteomics using NanoESI-LC-MS/MS.

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International Patent Organism Depositary (IPOD), National Institute of Advanced Industrial Science and Technology (AIST), Central 6, 1-1-1 Higashi, Tsukuba 305-8566, Japan.


In the present study, we profiled proteins in ssa1/2 mutant and wild-type using one-dimensional gel electrophoresis coupled with liquid chromatography and mass spectrometry to reveal a total of 322 proteins. Sixty and 84 nonredundant proteins were detected in ssa1/2 and wild-type, respectively, whereas 178 were common. A quantitative profiling proteomic approach using a modified N-terminal isotope tagging method was undertaken to determine quantitative changes in proteins between mutant and wild-type. Out of 210 identified proteins selected for quantification, 103 propionylated proteins were obtained. Eight only D0-propionylated protein (wild-type) and 4 only D5-propionylated proteins (ssa1/2) were detected; 90 proteins were overlapped in the ssa1/2 mutant and wild-type. In the ssa1/2 mutant, 28 proteins were up-regulated and 26 were down-regulated. The expression levels of the rest of 49 proteins were not changed compared with the wild-type. Furthermore, non-correlation between mRNA and protein expressions was found. Among up-regulated proteins, 19 proteins involved in protein synthesis, chromatin condensation, and silencing showed unchanged mRNA expression levels. Among down-regulated proteins, 21 proteins consisting mainly of transcription factors showed unchanged mRNA expressions. Surprisingly, several proteins involved in protein synthesis were also found among the down-regulated proteins. These results suggested that the proteins showing changed protein expressions and unchanged mRNA expressions were affected by the deletion of SSA1 and SSA2 genes at translational efficiency, mRNA degradation, or protein degradation. Moreover, we found the proteins related to chromosomal control were up-regulated in ssa1/2 mutant, a novel finding of this study, suggesting that the Ssa1/2p might contribute to chromosomal control.

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