Iodide is transported out of the thyroid cells across the apical membrane into the follicle by a chloride-iodide ion counter- transporter molecule called pendrin.

TLS Online TPP Program

#Id: 9461

#Unit 4. Cell Communication and Cell Signaling

Active JAK kinase phosphorylates several tyrosine residues in the receptor’s cytosolic domain and activates a STAT transcription factor that moves directly to the nucleus

TLS Online TPP Program

#Id: 9462

#Unit 4. Cell Communication and Cell Signaling

All STAT proteins contain: 

an N-terminal DNA-binding domain

an SH2 domain

a C-terminal domain with a critical tyrosine residue

TLS Online TPP Program

#Id: 9463

#Unit 4. Cell Communication and Cell Signaling

SH2 domain (Src homology 2 domain) 

homology with a region in the Src cytosolic tyrosine kinase encoded by the src gene.

TLS Online TPP Program

#Id: 9464

#Unit 4. Cell Communication and Cell Signaling

The SH2 domain binds strongly to short target peptides containing a critical four-residue core sequence:: 

phosphotyrosine–glutamic acid–glutamic acid–isoleucine

TLS Online TPP Program

#Id: 9466

#Unit 4. Cell Communication and Cell Signaling

Binding resembles the insertion of a two-pronged “plug” the phosphotyrosine and isoleucine side chains

of the peptide into a two-pronged “socket” in the SH2 domain.

TLS Online TPP Program

#Id: 9467

#Unit 4. Cell Communication and Cell Signaling

SH2 domain of STAT binds to a specific phosphotyrosine in the cytosolic domain of an activated receptor