Kinases, Phosphatases, and GTPases Flashcards
protein kinases
similar to GEF
enzymes that transfer a phosphate group onto a target protein; thereby changing protein function from inactive to active
similar to GEF
protein kinase steps
(1) protein kindse binds ATP as well as the target protein
(2) transfers a phosphate group
(3) the phosphorylated protein and the remaining ADP are released from the protein kinase
phosphorylated protein
can be acivated, deactivated, or can act as a signle for other proteins to pass the single on
phosphatease
similar to GAP
removes the phosphate group from a target phosphorylated protein
similar to GAP
phosphorylation
figure A
reversible protein modification that is regulated by a balance of kinase and phosphatease activity
figure A
protein kinase classification
phosphorylates (1) tyrosine, (2) serine, or (3) threonine; however serine and threonine kinases are often grouped into one category
GTPases (GTP-binding proteins)
enzymes that bing to GTP and hyrdolyse it to GDP; when bound to GTP → active conformation; when in bound to GDP → inactive state
GTPase steps
(1)
Ras protein
figure B
in GTP-bound form → activates and stimulates protein phsophorylations in the cell; most of the time is in inactive form waiting for signal to exchange GDP for GTP
figure B
GAP (GTPase-activating protein)
similar to a protein phosphatase
binds to Ras protein to hydrolyze its bound GTP to GDP
similar to a protein phosphatase
GEF (guanine nucleotide exchange factor)
similar to protein kinase
binds to GDP-Ras and causes Ras to release its GDP; the Ras binding site is then immidatly filled by a GTP molecule; thus the GEF indirectly activates Ras protein
similar to a protein kinase
