Question

22. which of the following activity is most likely leads to activation of protein kinase A?

a. activation of PLC by GBsubunits

b. cytosolic Ca++ changes

c. activation of PI3 kinase ans down stream Rac GTPase

d. activation if adenylyl cyclase by Ga subunit

23. after insulin or a growth factor such as EGF or PDGF binds to its receptor and the receptors from a dimer , what us the next immediate event?

a. the dimerized receptor acts as a kinase to phosphorylate one or more tyrosine residues on its dimerized partner.

b. the dimerized receptor acts as a kinase fo phosphorylate or or more serine or threonine residues on its dimerized partner

c. docking proteins bind directly to the receptor.

d. activating the Ras GTPase.

e. adaptor proteins bind to the receptor due to a conformational change.

Answer 1

Answer 22- d) activation of adenylyl cyclase by Ga subunit.

Reason-  It is associated with signal-transduction pathways. It consists of a regulatory subunit and a calalytic subunit.The alpha unit binds to adenylyl cyclase, which converts ATP into cyclic AMP. The cyclic AMP binds to a regulatory subunit , that leads to a conformational change. Thus the catalytic subunit becomes active. Thus protein kinase A get activates.

Answer 21- a) the dimerized receptor acts as a kinase to phosphorylate one or more tyrosine residues on its dimerized partner.

Reason- it is the part of the insulin transduction pathway. After insulin enters the blood stream, it binds with the alpha-subunit of the glycoprotein receptor, which causes activation of tryosine kinase domains on each of the two beta-subunit. This causes auto-phosphorylation of several tyrosine residues in the beta-subunits.