Four TAFs do have some intrinsic DNA binding ability: TAF4b, TAF12, TAF9, and TAF6 are (distant) homologs of histones H2A, H2B, H3, and H4, respectively.  TAF4b/TAF12 and TAF9/TAF6 form heterodimers using the histone fold motif

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#Unit 4. Cell Communication and Cell Signaling

Active Raf phosphorylates MEK on one or two serine residues in its activation loop, activating MEK kinase activity

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#Unit 4. Cell Communication and Cell Signaling

Constitutively active Raf kinase

a glutamic acid substitution for the valine at position 600

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#Unit 4. Cell Communication and Cell Signaling

MEK is a dual-specificity protein kinase

phosphorylates its target proteins on both tyrosine and serine/threonine

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#Unit 4. Cell Communication and Cell Signaling

In humans, there are three RAS, three Raf, two MEK, and two MAP proteins.

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#Unit 4. Cell Communication and Cell Signaling

Mammalian MAP kinases include  Jun N-terminal kinases and p38 kinases, which are activated by signaling pathways in response to various types of stresses

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#Unit 4. Cell Communication and Cell Signaling

Phosphorylation by MEK at Y-185 and T-183 in activation loop of MAP kinase leads to a marked conformational change & promotes MAP kinase activation and dimerization.