Question

wt cells Mutant A Mutant B Mitogen 120 KDa | 110 KDa 100 KDa- 65KDa Figure 1: Newly identified MAP kinase signaling pathway mutants exhibit opposite effects. WT, Mutant A, and Mutant B cells were (+), and were not (), exposed to a signaling pathway stimulatory mitogen. Random mutations introduced to CHO cells then downstream S-cyclin expression was monitored to indicated MAP kinase signaling pathway activation. Expression of S-cyclin (65 kDa) determined via Western blot.

Name at least two potential proteins within this pathway that could be Mutant A.

Explain why.

Answer 1

1. The mutant occurs in Gtpase activating protein (GAP) ehich normally inactivate Ras GTP to Ras GDP. Due to mutation in GAP protein the above mechanism not take place so RAS-GTP always presence leads to continuous expression of MAP kinase pathway.

2. Receptor tyrosine kinase is mutated in mitogen binding site, so the conformational change occurs, it looks like without mitogen also it continuously activate the MAP kinase.

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