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Binding of [H-3] serotonin to skeletal muscle actin
Abstract: We previously observed that the neurotransmitter 5â€hydroxytryptamine (5â€HT, serotonin) binds with high†and lowâ€affinity interactions to an actinâ€like protein prepared from rat brain synaptosomes. In this study, we examined its binding to highly purified actin obtained from rabbit skeletal muscle. Monomeric Gâ€actin bound serotonin with high and low affinities, exhibiting equilibrium dissociation constants (KD values) of 5 × 10−5M and 4 × 10−3M, respectively. The serotonin binding site on actin was distinct from those sites previously characterized for divalent cations, nucleotides, and cytochalasin alkaloids. The binding of serotonin (1 μM) to Gâ€actin was increased as much as 26â€fold by divalent cations. Potassium iodine (KI) increased the affinity of Gâ€actin for serotonin, KD values for this binding being 3 × 10−7M and 6 × 10−5M. Serotonin bound with even higher affinity to polymerized Fâ€actin, with KD values of 2 × 10−8M and 2 × 10−5M. However, the total number of binding sites on Fâ€actin was only about 4% of the number of Gâ€actin. The binding of serotonin (0.1 μM) to Gâ€actin could be inhibited by phenothiazines (1 μM) or reserpine (10 μM), but not by classical antagonists of serotonin receptors or by drugs that release serotonin or inhibit its uptake. The binding of serotonin to actin in vivo may participate in a contractile process related to neurotransmitter release. Copyright © 1985, Wiley Blackwell. All rights reserved
History
Publication title
Journal of NeurochemistryVolume
45Pagination
819-824ISSN
0022-3042Department/School
Menzies Institute for Medical ResearchPublisher
Wiley-Blackwell Publishing Ltd.Place of publication
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