Thermal stability of carp actin in its polymerized form |
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Authors: | Atsushi Ooi Tsuyoshi Okagaki |
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Institution: | (1) Faculty of Bioresources, Mie University, 1577 Kurimamachiya-cho, Tsu Mie, 514-8507, Japan |
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Abstract: | We investigated the thermal denaturation of carp F-actin by measuring the loss of polymerization ability. The thermal denaturation
rates of carp F-actin were at least 10-fold higher than those of chicken F-actin. Binding of tropomyosin thermally stabilized
carp F-actin with no appreciable change in activation energy, suggesting the instability was caused by a high frequency of
fragmentation of the actin filaments. A comparison of the critical concentration for polymerization suggested that the subunit–subunit
interactions of carp F-actin were indeed weaker than those of chicken F-actin. Furthermore, using fluorescence quenching we
showed that the nucleotide binding region of carp F-actin was in a more open conformation. Together, our results suggest that
the instability of carp F-actin is a function of both the rate of fragmentation and the dissociation of bound nucleotides. |
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