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Chapter 6C. Proteomics. 25 and 27 February, 2004. Structural and Functional Characterization in the Post-genomic era. Overview. Proteomics examines the collection of proteins present in a given type of cell at a given time.
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Chapter 6C Proteomics 25 and 27 February, 2004 Structural and Functional Characterization in the Post-genomic era.
Overview • Proteomics examines the collection of proteins present in a given type of cell at a given time. • Proteomics depends on genome sequences, but differs in the sense that the genome is static but the proteome changes over time. • Global analysis of proteomes involves measuring a large number of phenotypes or concentrations simultaneously. • The link between structure and function is tight, but not well understood. • Interactions between proteins form networks of functionality. Defining these networks is the most challenging goal of proteomics.
Pathway and localization information are available for the mTn mutant sets.
Uptag/Downtag deletion strategy generates unique tags at deletion site. Unique tags are flanked by sites for PCR amplification.
Phenotype assignment using tagged deletion strategy • Make a microarray containing UPTAG / DOWNTAG sequence. Each strain hybridizes to only one place on the microarray. • Grow mixtures of hundreds of strains in the same flask under different conditions. • Measure which strains grew by intensity of unique microarray hybridization of the PCR amplification of tags from all the strains present in the flask before and after growth. • Time zero = red, 6 hours later = green • No difference --> Yellow, Defect = Red
RNAi • Small dsRNA complementary to a gene will make expression of the protein product of that gene impossible. • Allows conditional knockouts in adult eukaryotes, especially C. elegans, where RNAi works even if the small dsRNA is eaten. • RNAi is one of the most significant advances in functional genetics. • New - first reported in 1998, just beginnning to be applied.
A high-throughput method to determine three dimensional crystal structure and relate it to function is a long-term goal of proteomics: an example from the Archaea
Protein interactions • Hard to detect since the rules are totally opaque • Interaction depends on structure in complex ways. • Empirical evidence is required. • Coimmunoprecipitation • High-throughput strategies • Protein microarrays • 2-hybrid interaction trap
Which proteins are present? Two-dimensional gel electrophoresis. Problems: Sample prep. Spot detection Quantification Identification
Assignment: Discovery Questions 1, 2, 5 ,6 ,9-13, 19, 20, 22-27, 35-39