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A researcher is interested in the proteins that E-cadrerin binds to. She expresses full-length E-cadherir as well some truncated constructs of the protein in a mouse cell line that does not express any other cadherins. The scheme of constructs is shown in figure A (E represents the extracelular comair, TM the transmembrane domain and C the cytoplasmic domain). She labels the cells with 35 methionine for 16 hours, homogenizes them in detergent, and an antibody raised against the extracellu ar domain of the cacherin C-cacherin to pull-down (co- immunoprecipitate) C-cadherin and any associated proteins. She then analyses the immune precipitates by electrophoresis by SDS-PAGC, followed by autoradiography to make the labelled proteins visible. In lane 1 of figure B, the antibody precipitates three major proteins in cells transfected with a pasmid expressing the full-length intact cadherin. These proteins are not precipitated from untreated control cells. H₂N E TM C A COOH 553aa 24 a aa m B kd 200 - 97 - 67- 45- www. m Full-length 31 aa 70 aa 105 aa 151 aa 37aa E-Cad 437 E-Cad 48 E-Cad 431 E-Cad 470 E-Cad 105 control 1 2 3 4 5 6 7 Full-length E-Cad 437 E-Cad 48 E-Cad 431 E-Cad 470 E-Cad A105 a. Which protein bands in the autoradiograph (Figure B) correspond to cacherir and which correspond to proteins that bind to cadherin? Explain your answer. (2 marks) b. Which segment of cadherin is responsible for binding to other proteins? (2 marks) c. With what is known about cadherin complexes, speculate on the possible identity of the immunoprecipitated proteins. (1 mark)