Practice Questions

TLS Online TPP Program

#Question id: 1262

Although MAP kinase is often activated in multicellular animals by RTKs or cytokine receptors, signaling from other receptors can activate MAP kinase in other eukaryotic cells. we consider the mating pathway in the yeast S. cerevisiae, a well-studied example of a MAP kinase cascade linked to G protein–coupled receptors (GPCRs). Which of the following statement is incorrect?

#Unit 4. Cell Communication and Cell Signaling

An a haploid cell secretes the a mating factor and has GPCRs for the α factor on its cell surface; an α cell secretes the α factor and has GPCRs for the a factor. Thus each type of cell recognizes the mating factor produced by the opposite type.
Ligand binding and dissociation of the G protein subunits, the membrane-tethered Gβγ subunit binds the Ste5 scaffold to the plasma membrane.
Gβγ also activates Cdc24, a GAP for the Ras-like protein Cdc42; the active, GTP-bound Cdc42, in turn, binds to and activates the Ste20 kinase.
Ste20 then phosphorylates and activates Ste11, which is analogous to Raf and other mammalian MEK kinase (MEKK) proteins. Ste20 thus serves as a MAPKKK kinase.