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F-actin-like ATPase Activity in a Polymerization-defective Mutant Yeast Actin (V266G/L267G)
Journal article   Open access   Peer reviewed

F-actin-like ATPase Activity in a Polymerization-defective Mutant Yeast Actin (V266G/L267G)

Xiaoyi Yao and Peter A Rubenstein
The Journal of biological chemistry, Vol.276(27), pp.25598-25604
07/06/2001
DOI: 10.1074/jbc.M011797200
PMID: 11328808
url
https://doi.org/10.1074/jbc.M011797200View
Published (Version of record) Open Access

Abstract

Polymerization increases a low level G-actin ATPase activity yielding ADP-P(i) F-actin and then ADP F-actin following release of P(i). By monitoring P(i) release, we explored the relationship between the ATPase activity and polymerization characteristics of a mutant yeast actin, GG. In this mutant, two hydrophobic residues at the tip of a proposed hydrophobic plug between actin subdomains 3 and 4, Val(266) and Leu(267), were mutated to Gly. Although GG-actin does not polymerize by itself in vitro, GG cells are viable. We show that GG-actin ATPase activity increases under normal polymerization conditions, although stable filaments do not form. A plot of P(i) release rate versus actin concentration yields an apparent critical concentration, like that seen for actin polymerization, of approximately 8 microm for Mg(2+) GG-actin and 11 microm for Ca(2+) GG-actin. In contrast to WT-actin, P(i) release from GG-actin is cold-sensitive, reflecting the temperature sensitivity associated with mutations that decrease hydrophobicity in this region. Thus, under polymerization conditions, GG-actin exhibits a continuous F-actin-like ATPase activity resulting from the temperature-sensitive formation of unstable cycling F-actin oligomers. Tropomyosin limits the extent and rate of this activity and restores polymerization by capturing and stabilizing these oligomers rather than enhancing filament nucleation.

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