The bi-directional regulation of filamin on the ATPase activity of smooth muscle myosin.
OBJECTIVE
The aim of this study is to investigate the functional relationship between filamin, a known actin binding protein, and myosin and the effects of filamin on the interaction between myosin and actin.


METHODS
Ultra-centrifugation method was used to investigate the binding of filamin to both phosphorylated and unphosphorylated myosins. Mg-ATPase activities of both phosphorylated and unphosphorylated myosins in the presence and absence of actin were measured to observe the effects resulted from filamin-actin and filamin-myosin interactions.


RESULTS
It was found that filamin is also a myosin binding protein. Filamin inhibited the actin activated Mg-ATPase activity of phosphorylated myosin and stimulated Mg-ATPase of phosphorylated myosin in the absence of actin; in addition, filamin stimulated Mg-ATPase activity of unphosphorylated myosin in both the presence or absence of actin.


CONCLUSIONS
The result suggest that the effects of filamin on the myosin Mg-ATPase activities are bi-directional, i.e., stimulatory via binding to myosin and inhibitory via binding to actin.
Lin
Y
Y
Department of Pharmacology, Dalian Medical University, Dalian 116027.
Sun
H
H
Dai
S
S
Tang
Z
Z
He
X
X
Chen
H
H
D000199:Actins / Q000378:metabolism; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism*; D002645:Chickens; D003285:Contractile Proteins / Q000494:pharmacology*; D004789:Enzyme Activation; D064448:Filamins; D005895:Gizzard, Avian / Q000201:enzymology*; D008840:Microfilament Proteins / Q000494:pharmacology*; D010766:Phosphorylation; D024745:Smooth Muscle Myosins / Q000378:metabolism*
D000199:Actins; D003285:Contractile Proteins; D064448:Filamins; D008840:Microfilament Proteins; D017301:Ca(2+) Mg(2+)-ATPase; D024745:Smooth Muscle Myosins