Question

 

1. A receptor tyrosine kinase (RTK) has a non-functioning kinase domain

Enhanced or Reduced

2. A G-protein whose α-subunit has a higher than normal binding affinity for GTP and a normal binding affinity for GDP.

Enhanced or Reduced

3. Protein Kinase A whose regulatory subunits cannot bind cAMP

Enhanced or Reduced

4. IP3 cannot bind to ER-calcium channels

Enhanced or Reduced

5. Notch cannot be cleaved following binding to Delta

Enhanced or Reduced

6. Sodium orthovanadate, a phosphatase inhibitor, is added to cells that have been stimulated with EGF

Enhanced or Reduced

7. Adenylyl cyclase cannot bind ATP

Enhanced or Reduced

8. GAP is hyperactivated

Enhanced or Reduced

 

Answer 1

1. RECEPTOR TYROSIN KINASE: RTK have cytosolic kinase domain. Which in lignad binding in the extracellutal domain causes autophosphorylation of kinase domain. Causes activation of the receptor. Which further phosphorylates a number of target protein. So, dis functional kinase domain reduce activity.
2. GPCR: alpha subunit of the G-protein bind to the GDP in inactive state. For activation G-protein attached to the GTP. So, inhanced affinity for GTP leads to enhancement of the activity.
3. PROTEIN KINASE A: PKA in inactive state consist of 4 subunits, two catalytic and two regulatory subunit. For activation cAMP bind to the regulatory subunits and cause dissociation of the catalytic part from the regulatory subunits. And get acivated. So, inability of thecAMP to bind to regulatory subunit cause reduction of function.
4. IP3: it bind to calcium from the ER and release it into the cell. So, unable of binding of Ca+ with the IP3 reduce the activity of cell.
5. ADENYL CYCLASE: this is an enzyme that covert ATP to cAMP by cleavage of pyrophosphate. Unability of binding to ATP reduce production of cAMP.
6. GAP: it si also known as GTPase activating protein or RGS- regulation of G protein. GAP activate Gprotein activity. So, hyperactive GAP cause hyperactivity of G-protein.
7. PHOSPHODIESTERASE: this PDE enzyme is an effector molecule for GPCR like receptor in eye. When light fall on the eye and the signal is transmitted by the rod cell and activate the GPCR like receptor which causes activation of transducin molecule. this transducin a the activate PDE enzyme. PDE then convert all the available cGMP to 5'GMP. this cause fall of conc of the cGMP in cytosol. after that all the CGMP bound Na+ channel are closed to release cGMP in the cell to increase conc. This cause hyperpolarization of the rod cell and can feel light perception. So introduction of PDE enzyme inhibitor leads to reduced vision.
8. CALCIUM CHEALATOR: Ca+ act as a secondary messenger in GPCR. so chelator reduce GPCR activity.