Electron microscopic particle length of F-actin polymerized in vitro.
About: This article is published in Journal of Biochemistry.The article was published on 1970-03-01. It has received 145 citations till now.
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TL;DR: 2 microM CB strongly reduces the low shear viscosity of actin filaments alone and actin Filaments cross-linked by a variety of macromolecules, which may be due to inhibition of act in filament-filament interactions which normally contribute to network formation.
706 citations
TL;DR: It is found that the net result of four association and four dissociation steps is a lengthening of the filament by one protomer at one end and a corresponding shortening at the other.
703 citations
TL;DR: In the case of muscle there is clear evidence that the TM moves its position on the F-actin filament during contraction and it is therefore considered to play an important part in the regulation of the process.
Abstract: Tropomyosin (TM) is widely distributed in all cell types associated with actin as a fibrous molecule composed of two α-helical chains arranged as a coiled-coil. It is localised, polymerised end to end, along each of the two grooves of the F-actin filament providing structural stability and modulating the filament function. To accommodate the wide range of functions associated with actin filaments that occur in eucaryote cells TM exists in a large number isoforms, over 20 of which have been identified. These isoforms which are expressed by alternative promoters and alternative RNA processing of four genes, TPM1, 2, 3 and 4, all conform to a general pattern of structure. Their amino acid sequences consist of an integral number, six or seven in vertebrates, of quasiequivalent regions of about 40 residues that are considered to represent the actin-binding regions of the molecule. In addition to the variable regions a large part of the polypeptide chains of the TM isoforms, mainly centrally located and expressed by five exons, is invariant. Many of the isoforms are tissue and filament specific in their distribution implying that the exons expressed in them and the regions of the molecule they represent are of significance for the function of the filament system with which they are associated. In the case of muscle there is clear evidence that the TM moves its position on the F-actin filament during contraction and it is therefore considered to play an important part in the regulation of the process. It is uncertain how the role of TM in muscle compares to that in non-muscle systems and if its function in the former tissue is unique to muscle.
470 citations
TL;DR: It is suggested that actin filaments can accelerate the rate of polymerization of G-actin in low ionic strength medium by providing sites onto which actin monomers can be added, and that cytochalasins inhibit actin filament elongation by binding to high affinity sites located at the polymerization end of the filaments.
420 citations
TL;DR: Turbidometric measurements of the kinetics of filament assembly revealed a biphasic mechanism, involving the initial rate-limiting formation of a hexamer nuclear particle followed by a more rapid rate of polymerization to filaments.
363 citations