title: A comparative proteomic strategy for subcellular proteome research: ICAT approach coupled with bioinformatics prediction to ascertain rat liver mitochondrial proteins and indication of mitochondrial localization for catalase.
abstract: Subcellular proteomics, as an important step to functional proteomics, has been a focus in proteomic research. However, the co-purification of "contaminating" proteins has been the major problem in all the subcellular proteomic research including all kinds of mitochondrial proteome research. It is often difficult to conclude whether these "contaminants" represent true endogenous partners or artificial associations induced by cell disruption or incomplete purification. To solve such a problem, we applied a high-throughput comparative proteome experimental strategy, ICAT approach performed with two-dimensional LC-MS/MS analysis, coupled with combinational usage of different bioinformatics tools, to study the proteome of rat liver mitochondria prepared with traditional centrifugation (CM) or further purified with a Nycodenz gradient (PM). A total of 169 proteins were identified and quantified convincingly in the ICAT analysis, in which 90 proteins have an ICAT ratio of PM:CM>1.0, while another 79 proteins have an ICAT ratio of PM:CM<1.0. Almost all the proteins annotated as mitochondrial according to Swiss-Prot annotation, bioinformatics prediction, and literature reports have a ratio of PM:CM>1.0, while proteins annotated as extracellular or secreted, cytoplasmic, endoplasmic reticulum, ribosomal, and so on have a ratio of PM:CM<1.0. Catalase and AP endonuclease 1, which have been known as peroxisomal and nuclear, respectively, have shown a ratio of PM:CM>1.0, confirming the reports about their mitochondrial location. Moreover, the 125 proteins with subcellular location annotation have been used as a testing dataset to evaluate the efficiency for ascertaining mitochondrial proteins by ICAT analysis and the bioinformatics tools such as PSORT, TargetP, SubLoc, MitoProt, and Predotar. The results indicated that ICAT analysis coupled with combinational usage of different bioinformatics tools could effectively ascertain mitochondrial proteins and distinguish contaminant proteins and even multilocation proteins. Using such a strategy, many novel proteins, known proteins without subcellular location annotation, and even known proteins that have been annotated as other locations have been strongly indicated for their mitochondrial location.
authors.affiliation: Research Centre for Proteome Analysis, Key Lab of Proteomics, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Graduate School of the Chinese Academy of Sciences, Shanghai 200031, China.
authors.forename: Xiao-Sheng
authors.initials: XS
authors.lastname: Jiang
authors.forename: Jie
authors.initials: J
authors.lastname: Dai
authors.forename: Quan-Hu
authors.initials: QH
authors.lastname: Sheng
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.forename: Qi-Chang
authors.initials: QC
authors.lastname: Xia
authors.forename: Jia-Rui
authors.initials: JR
authors.lastname: Wu
authors.forename: Rong
authors.initials: R
authors.lastname: Zeng
mesh_terms: D000818:Animals; D002374:Catalase / Q000032:analysis* / Q000378:metabolism; D019295:Computational Biology; D008401:Gas Chromatography-Mass Spectrometry; D008930:Mitochondria, Liver / Q000737:chemistry* / Q000201:enzymology / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000032:analysis* / Q000378:metabolism; D020543:Proteome / Q000032:analysis* / Q000378:metabolism; D040901:Proteomics / Q000379:methods*; D051381:Rats
chemical_list: D024101:Mitochondrial Proteins; D020543:Proteome; D002374:Catalase