A maintenance methyltransferase acts constitutively only on hemimethylated sites to convert them to fully methylated sites. Its existence means that any methylated site is perpetuated after replication.  There is one maintenance methyltransferase (Dnmt1) in mice, and it is essential.

TLS Online TPP Program

#Id: 1362

#Unit 4. Cell Communication and Cell Signaling

In cytokine receptors, the tightly bound kinase is known as a JAK kinase.

TLS Online TPP Program

#Id: 1363

#Unit 4. Cell Communication and Cell Signaling

JAK kinases become activated after ligand binding and receptor dimerization.

TLS Online TPP Program

#Id: 1364

#Unit 4. Cell Communication and Cell Signaling

Phosphorylation of the activation loop leads to a conformational change in the JAK kinase that enhances the affinity of the enzyme for ATP & increasing kinase activity.

TLS Online TPP Program

#Id: 1365

#Unit 4. Cell Communication and Cell Signaling

JAK kinases phosphorylate several tyrosine residues on the cytosolic domain of the cytokine receptor.

TLS Online TPP Program

#Id: 1366

#Unit 4. Cell Communication and Cell Signaling

Phosphotyrosines function as docking sites for STAT proteins.

TLS Online TPP Program

#Id: 1367

#Unit 4. Cell Communication and Cell Signaling

All STAT proteins contain: 

An N-terminal DNA-binding domain

An SH2 domain