Exchange of the actin-bound nucleotide in intact arterial smooth muscle.
The actin-bound ADP was separated from cytoplasmic nucleotides by treatment of intact arterial smooth muscle with 50% ethanol. In (32)P-labeled smooth muscle the actin-bound ADP and phosphate readily exchanged with the cytoplasmic [gamma,beta-(32)P]ATP; the specific radioactivity of actin-bound ADP was equal to that of the beta-phosphate of cytoplasmic ATP and the specific radioactivity of actin-bound phosphate was equal to that of the gamma-phosphate of cytoplasmic ATP. In contrast, the exchange of the actin-bound ADP in skeletal muscle was very slow. The presence of cytoplasmic ATP was required for the exchange of the actin-bound ADP and phosphate; if ATP synthesis was inhibited the exchange was also inhibited. The extent of exchange was reduced in muscles contracted by histamine or K(+), as compared with resting muscles. The exchange was also shown in other mammalian smooth muscles, uterus, urinary bladder, and stomach. The data indicate a dynamic state of actin in smooth muscle. The data also suggest that polymerization-depolymerization of actin is part of the contraction-relaxation cycle of smooth muscle.
Bárány
M
M
Department of Biochemistry, University of Illinois College of Medicine, Chicago, Illinois 60612, USA. mbarany@uic.edu
Barron
J T
JT
Gu
L
L
Bárány
K
K
D000199:Actins / Q000378:metabolism*; D000244:Adenosine Diphosphate / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002339:Carotid Arteries / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D011485:Protein Binding; D051381:Rats; D013552:Swine
D000199:Actins; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate