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High Throughput and Large Scale Proteomics Analysis. Austin Yang, Ph.D. Department of Pharmaceutical Sciences, University of Southern California. Overview. Shotgun proteomics and ESI mass spectrometry Proteomic data mining and data visualization. 12,000 proteins.
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High Throughput and Large Scale Proteomics Analysis Austin Yang, Ph.D. Department of Pharmaceutical Sciences, University of Southern California
Overview • Shotgun proteomics and ESI mass spectrometry • Proteomic data mining • and data visualization
Are We Ready for Mammalian Proteomics ? Shotgun Proteomics 2-D Gel Cytoskelatal Proteins mM, 1x 109 copies/cell Metabolism 0.1 mM, 1x 108 Ribosomes 10 mM, 1x 107 Kinases 1 mM, 1x 106 Cyclins 0.1 mM, 1x 105 Transcription factors 10 nM, 1x 104 Synaptic Markers 0.1 nM, 1x 103
Advantages of Proteomics Using LC-MS/MS • No pre-selection of biased targets • (hypothesis-free, open approach) • Protein variants are detected simultaneously • Protein isolation and detection are on a small scale (~ 10 fmol from complex mixtures – subcellular fractions, whole cells, or tissue) • Obtain sequence information of peptides (not just masses) and can sequence ~4,000 proteins in a single experiment
Liquid Chromatography Quadrupole Ion Trap Tandem Mass Spectrometer
0-500 mM NH4OAc 500 SCX Column 400 300 200 100 RP #1 RP #2 300 500 200 400 100 1,000-2,000 Sequencing Attempts in 60 Minutes Multidimensional Protein Identification Technology (MudPIT) Digested protein complexes 20,000 MS/MS spectra/day
Electrospray Ionization (ESI) Ions in gaseous phase Ions in solution LC Spray tip Ion source opening for the MS
Theoretical CID of a Tryptic Peptide y1 y3 b1 y2 b2 b3 MS/MS Spectrum K G L F K F L G + + + + F L G K + + F L G K b3 y1 F L G K + + + + Parent ions F L G K F L G K CID b2 y2 + F L G K + + + + F L G K F L G K b1 y3 Non-dissociated Parent ions Daughter ions Relative Intensity m/z (464.29)
Data Mining through SEQUEST and PAULA • DatabaseSearch Time • Yeast ORFs (6,351 entries) 52 sec: 0.104 sec/s • Non-redundant protein (100k entries) 3500 min: • EST (100K entries, 3-frames) 5-10,000 min:
STEP 1. SEQ 1 SEQ 2 SEQ 3 SEQ 4 STEP 3. SEQUEST Algorithm Theoretical MS/MS spectra Step 1. Determine Parent Ion molecular mass Step 2. 500 peptides with masses closest to that of the parent ion are retrieved from a protein database. Computer generates a theoretical MS/MS Spectrum for each peptide sequence (SEQ1, 2, 3, 4, …) (Experimental MS/MS Spectrum) ZSA-charge assignment Step 4. Scores are ranked and Protein Identifications are made based on these cross correlation scores. Step 3. Experimental Spectrum is compared with each theoretical spectra and correlation scores are assigned. (Experimental MS/MS Spectrum) Unified Scoring Function
One spectrum TWO protein identifications Spectrum A was used to search against NCBI human database: Macrophage inhibitory factor was identified Same spectrum was used to search against non-redundant database. Bovine G-protein gamma was identified. Since the primary amino acid sequence of human G-protein gamma is almost identical to bovine, this protein was later identified as human G-protein Gamma. The initial false ID was due to an entry missing of human g-protein in human database. The sequence was later reentered Into the human database and the third search yielded correct ID. Mol Cell Proteomics. 2003 Jul;2(7):428-42. Fragment ions match both sequences are indicated by * Spectrum B has two additional ions matched to G-protein gamma
Distribution of Xcorr from correctly and incorrectly identified peptides
Proteomic Data Visualization and Future Directions • information overload • data integration • ease of visualization
Network for NMDA and glutamate receptors (Zoom-in)
SEQUEST SALSA Raw Unidentified Spectra (~10,000-100,000) Identified Sequence Scoring Algorithm for Spectral Analysis
SALSA Overview * • SALSA is a tool for identifying MS-MS spectra in Xcalibur analysis files that display specific user-defined characteristics. Because these characteristics correspond to structural features of a peptide, SALSA allows the user to selectively locate MS-MS spectra of specific peptides or their variant or modified forms. product ion loss charged Massdifference neutralloss A G D W T ion series
Construction of SALSA ruler GAIIGLMGGVV m/z GAIIGLMGGV GAIIGLMGG GAIIGLMG GAIIGLMGGVV GAIIGLM GAIIGL GAIIG GAII GAI GA GAIIGLMGGV GAIIGLMGG GAIIGLMG GAIIGLMGGVV GAIIGLM GAIIGL GAIIG GAII Methionine Oxidation 16 amu (one oxygen atom) GAI GA
Absolute Quantification Analysis Quantification of Methionine Oxidation GAIIGLMVGGVV GAIIGLMVGGVV: +7 amu