Characterization of calcium-binding light chain as a Ca(2+)-receptive subunit of Physarum myosin.
Physarum myosin is uniquely under an inhibitory Ca(2+)-regulation in the ATP-dependent interaction with actin [Kohama (1990) Trends Pharmacol. Sci. 11, 433-435, for review]. Calcium-binding light chain (CaLc) has been suggested to be of primary importance to the control from its amino acid sequence [Kobayashi et al. (1988) J. Biol. Chem. 263, 305-313]. To provide a biochemical basis for this suggestion, the Ca-binding capacity of CaLc and its Kd for Ca2+ were measured. The Ca-binding properties of CaLc allowed those of Physarum myosin to be explained in terms of CaLc. However, the mode of Ca(2+)-regulation by CaLc differs according to the enzyme upon which Ca-sensitivity is confered by CaLc, i.e., CaLc activated bovine phosphodiesterase activity and inhibited Physarum myosin ATPase activity, with the same Kd in microM levels. Thus, CaLc appears to work as a mere Ca-receptive subunit in Physarum myosin, with the secret of the inhibition lying in other subunits. CaLc was also shown to belong to a family of alkali light chains (AlLc) by allowing it to bind skeletal myosin as a substitute for its AlLc. Therefore, present study is the first biochemical indication that the AlLc family is involved in regulating the myosin function.
Kohama
K
K
Department of Pharmacology, Gunma University School of Medicine.
Okagaki
T
T
Takano-Ohmuro
H
H
Ishikawa
R
R
D000199:Actins / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002135:Calcium-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism; D004228:Dithionitrobenzoic Acid / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D007700:Kinetics; D046911:Macromolecular Substances; D008970:Molecular Weight; D009218:Myosins / Q000378:metabolism*; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D016839:Physarum polycephalum / Q000378:metabolism*; D014268:Trifluoperazine / Q000494:pharmacology
D000199:Actins; D002135:Calcium-Binding Proteins; D002147:Calmodulin; D046911:Macromolecular Substances; D014268:Trifluoperazine; D004228:Dithionitrobenzoic Acid; D010727:Phosphoric Diester Hydrolases; D009218:Myosins; D002118:Calcium