J. Biol. Chem., Vol. 263, Issue 10, 4532-4536, Apr, 1988
The effect of filament shortening on the mechanical properties of gel- filtered actin
KS Zaner and JH Hartwig
Massachusetts General Hospital, Department of Medicine, Harvard Medical School, Boston 02114.
To address the claim that filaments polymerized from highly purified
(gel-filtered) F-actin acquire the elastic properties of a solid
attributable to chemical cross-linking, we measured the rheologic spectrum
of the dynamic storage modulus, G', and loss modulus, G'' from 5 x 10(-4)
to 0.5 Hz for gel-filtered actin alone and in the presence of the actin
shortening protein, gelsolin. We confirmed that gel- filtered filamentous
actin is a highly elastic material as evidenced by a relatively
frequency-independent G', which is consistent with either topologically
constrained filaments or a chemically cross-linked gel. Introduction of
gel-filtered actin oligomers, however, caused the behavior of gel-filtered
actin to become more frequency-dependent and almost identical to that of
non-gel-filtered actin, suggesting that the effect of gel filtration on the
mechanical behavior of actin is topologic. This conclusion is further
supported by the finding that shortening of the actin filaments by the
addition of gelsolin at molar ratios to actin of from 1:8000 to 1:500
causes a gradual decrease in elasticity and increase in the amount of flow.
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