MoBio Signaling via Cell-Surface Enzymes Chapter 6

Signaling enzymes which are cell-surface receptors

Receptor tyrosine kinase

Receptor tyrosine kinases play a key role in cellular processes. A tyrosine kinase catalyzes the phosphorylation of tyrosine residues in a protein. The phosphorylated protein can then pass the signal to SH2-containing proteins.


Figure 6-E-1. The phosphate group of phosphotyrosine (phosphorylated tyrosine) can form several hydrogen bonds with the SH2 (Src homology 2) domain of some proteins involved in the signaling via tyrosine kinases.


Figure 6-E-2. Domain structure of some SH2-containing proteins.

Receptor serine/threonine kinase

Example: TGF-β. It is a growth factor with broad tissue distribution that plays critical roles during embryonic development, normal tissue homeostasis, and cancer (reference).

Receptor tyrosine phosphatase

It catalyzes the dephosphorylation of the tyrosine residue.

Receptor guanylyl cyclase

It catalyzes the synthesis of cGMP.

Signaling enzymes anchored on the cytosolic face of the plasma membrane

Non-receptor tyrosine kinases

Three major classes of non-receptor tyrosine kinases have been identified: Src, Abl and Jak.