Lehman W, Szent-Györgyi G. Activation of the adenosine triphosphatase of Limulus polyphemus actomyosin by tropomyosin.
J Gen Physiol 1972;
59:375-87. [PMID:
4260494 PMCID:
PMC2203184 DOI:
10.1085/jgp.59.4.375]
[Citation(s) in RCA: 52] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Purified actin does not stimulate the adenosine triphosphatase (ATPase) activity of Limulus myosin greatly. The ATPase activity of such reconstituted preparations is only about one-fourth the ATPase of myofibrils or of natural actomyosin. Actin preparations containing tropomyosin, however, activate Limulus myosin fully. Both the tropomyosin and the actin preparations appear to be pure when tested by different techniques. Tropomyosin combines with actin but not with myosin and full activation is reached at a tropomyosin-to-actin ratio likely to be present in muscle. Tropomyosin and actin of several different animals stimulate the ATPase of Limulus myosin. Tropomyosin, however, is not required for the ATPases of scallop and rabbit myosin which are fully activated by pure actin alone. Evidence is presented that Limulus myosin, in the presence of ATP at low ionic strength, has a higher affinity for actin modified by tropomyosin than for pure actin.
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