Biochemical characterization of a casein kinase I-like actin kinase responsible for the actin-induced suppression of casein kinase II activity in vitro.
By combination of column chromatographies (heparin-agarose, HiTrap heparin and HiTrap SP columns) and gel filtration on a Superdex 200-pg HPLC column, an actin kinase was partially purified from a 1. 5 M NaCl extract of porcine liver. The actin kinase was finally purified, by actin-Sepharose column chromatography (HPLC), as an actin-binding protein kinase. The biochemical properties, such as (1) requirements of divalent cations (10 mM Mg(2+) and 3 mM Mn(2+)) and effective phosphate acceptors (actin and alpha-casein), (2) phosphorylation of both Ser- and Thr-residues on these two phosphate acceptors, (3) autophosphorylation of the catalytic subunit (approximately 37 kDa), and (4) inhibition kinetics by CK-I-7 (a CK-I specific inhibitor), of the purified actin kinase were similar to those reported for CK-I purified from various mammalian cells, but it was distinguishable from three cellular actin kinases (A-kinase, C-kinase and actin-fragmin kinase (approximately 80 kDa)). The 37 kDa actin kinase-mediated phosphorylation of actin did not relate to its polymerizability. Inhibition of CK-II-mediated phosphorylation of functional cellular proteins, including calmodulin (CaM), by actin was significantly stimulated after its full phosphorylation by the purified 37 kDa actin kinase or rCK-I in vitro. These results suggest that: (1) the 37 kDa Ser/Thr actin-binding kinase may be classified as a member of the CK-I family; and (2) specific phosphorylation of actin by the actin kinase may be involved in the suppression mechanism of CK-II-mediated signal transduction at the cellular level.
Karino
A
A
Laboratory of Genetical Biochemistry, Kitasato University School of Allied Health Sciences, Kitasato 1-15-1, Sagamihara, Japan.
Okano
M
M
Hatomi
M
M
Nakamura
T
T
Ohtsuki
K
K
D000199:Actins / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D047388:Casein Kinases; D002413:Cations, Divalent; D002851:Chromatography, High Pressure Liquid; D015536:Down-Regulation; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008099:Liver / Q000201:enzymology; D010766:Phosphorylation; D011487:Protein Conformation; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000302:isolation & purification / Q000378:metabolism*; D013379:Substrate Specificity; D013552:Swine
D000199:Actins; D002413:Cations, Divalent; D011494:Protein Kinases; C074377:actin kinase; D047388:Casein Kinases; D017346:Protein Serine-Threonine Kinases