F-actin-like ATPase activity in a polymerization-defective mutant yeast actin (V266G/L267G).
J Biol Chem
; 276(27): 25598-604, 2001 Jul 06.
Article
in En
| MEDLINE
| ID: mdl-11328808
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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Collection:
01-internacional
Database:
MEDLINE
Main subject:
Actins
/
Adenosine Triphosphatases
Language:
En
Journal:
J Biol Chem
Year:
2001
Document type:
Article
Affiliation country:
United States