Casein kinase II beta-subunit inhibits the activity of the catalytic alpha-subunit in the absence of salt.
Casein kinase II (CKII) has a subunit structure of alpha 2 beta 2 where alpha is the catalytic subunit. Recombinant Drosophila casein kinase II alpha-subunit expressed in insect cells is inhibited by NaCl, thermally labile and inactivated by binding to plastic. In the presence of detergent (Tween 80) recombinant alpha-subunit has a kcat of 249 min-1 (Km 170 microM) for the peptide substrate RRRDDDSDDD-NH2, compared to recombinant Drosophila CKII with a kcat of 71 min-1 (per mol alpha) (Km 42 microM) and bovine CKII with a kcat of 123 min-1 (per mol alpha) (Km 45 microM) when measured in the absence of NaCl. The kcat values of bovine CKII and recombinant Drosophila CKII measured in the presence of 150 mM NaCl were 429 min-1 (per mol alpha) (Km 82 microM) and 204 min-1 (per mol alpha) (Km 51 microM), respectively. Since the kcat for the Drosophila alpha-subunit is approx. 3-fold greater than the Drosophila CKII measured in the absence of added salt these results indicate that the beta-subunit acts primarily as an inhibitory subunit.
Tiganis
T
T
St. Vincent's Institute of Medical Research, Fitzroy, Vic., Australia.
House
C M
CM
Kemp
B E
BE
D000595:Amino Acid Sequence; D000818:Animals; D047390:Casein Kinase II; D002384:Catalysis; D002460:Cell Line; D004330:Drosophila / Q000201:enzymology*; D007700:Kinetics; D008969:Molecular Sequence Data; D009036:Moths; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D012965:Sodium Chloride; D013379:Substrate Specificity
D011994:Recombinant Proteins; D012965:Sodium Chloride; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases