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HERO ID
7631966
Reference Type
Journal Article
Title
Electrostatic effects of smooth muscle calponin on actin assembly
Author(s)
Tang, JX; Szymanski, PT; Janmey, PA; Tao, T; ,
Year
1997
Is Peer Reviewed?
Yes
Journal
European Journal of Biochemistry
ISSN:
0014-2956
EISSN:
1432-1033
Publisher
WILEY
Location
HOBOKEN
Page Numbers
432-440
Language
English
PMID
9249057
DOI
10.1111/j.1432-1033.1997.00432.x
Web of Science Id
WOS:A1997XJ24700056
URL
http://doi.wiley.com/10.1111/j.1432-1033.1997.00432.x
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Abstract
The contribution of electrostatic interactions to the effects of chicken gizzard calponin on the kinetics of actin polymerization and the bundling of F-actin were characterized by a combination of fluorescence, light-scattering, co-sedimentation, and electron-microscopic methods. Stoichiometric amounts of calponin accelerate actin polymerization in low-ionic-strength solutions, but this effect is diminished at [KCI] = 150 mM. At low ionic strengths, micromolar concentrations of calponin induce the formation of large bundles of actin filaments, and lower concentrations of calponin quench the fluorescence of pyrene-labeled F-actin. The latter effect is related to binding of calponin to F-actin rather than to bundling of the filaments. The concentration of calponin required to bundle a fixed concentration of actin filaments increases with increasing ionic strength, as the average diameter of the bundles decreases. Millimolar concentrations of ATP, GTP or ITP are equally efficient at dispersing actin bundles to single filaments or smaller aggregates, even though a significant fraction of calponin remains bound to F-actin. Our findings show that the binding of calponin to actin is determined at least in part by electrostatic interactions, and that the polycationic nature of calponin is primarily responsible for the formation of F-actin bundles via its ability to reduce the electrostatic repulsion between the negatively charged actin filaments.
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