You performed a co-immunoprecipitation experiment to identify cellular proteins associated with protein X. For the experiment, you used antibodies against protein X that were immobilized on beads. You incubated these beads with cell lysates from either wild-type cells or cells lacking the gene encoding protein Y. After washing and eluting the bound protein off the beads, you separated each bound and unbound fraction by SDS-PAGE. Finally, you performed immunoblotting using antibodies against either protein Y or protein Z. The results of the Western blots are presented in the following schematic drawings. According to these results, do you think protein Y enhances (E) or inhibits (I) binding of protein X to protein Z? Write down E or I as your answer.

Question

Quizplus · Accepted Answer

Protein Z is found in the bound fraction of wild-type cell lysates, but mostly in the unbound fraction of lysates lacking protein Y. Thus, protein Y, which itself associates with protein X, appears to promote binding of protein X to protein Z.

You Performed a Co-Immunoprecipitation Experiment to Identify Cellular Proteins Associated