Interaction in vivo and in vitro between the yeast fimbrin, SAC6P, and a polymerization-defective yeast actin (V266G and L267G)
A mutant yeast actin (GG) has decreased hydrophobicity in a subdomain 3/4 hydrophobic plug believed to be involved in a hydrophobic cross-strand âplug-pocketâ interaction necessary for actin filament stability. This actin will not polymerize in vitro but is compatible with cell viability. We hav...
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Veröffentlicht in: | The Journal of biological chemistry 1999-12, Vol.274 (50), p.35873-35880 |
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Sprache: | eng |
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Zusammenfassung: | A mutant yeast actin (GG) has decreased hydrophobicity in a subdomain 3/4 hydrophobic plug believed to be involved in a hydrophobic
cross-strand âplug-pocketâ interaction necessary for actin filament stability. This actin will not polymerize in vitro but is compatible with cell viability. We have assessed the ability of Sac6p, the yeast homologue of the actin filament stabilizing
and bundling protein fimbrin, to restore polymerization in vitro and to facilitate GG-actin function in vivo . Sac6p rescues GG-actin polymerization at 25â°C but not at 4â°C. The actin polymerizes into bundles at room temperature with
a fimbrin:actin molar ratio of 1:4. At this ratio, every actin monomer contacts a Sac6p actin binding domain. Following cold-induced
depolymerization, actin/Sac6p mixtures repolymerize beginning at 15â°C instead of the 25â°C required for de novo assembly, because of the presence of residual actin-Sac6p nuclei. Generation of haploid Îsac6/GG-actin cells from either
diploid or haploid cells was unsuccessful. The facile isolation of cells with either mutation alone indicates a synthetic
lethal relationship between this actin allele and the SAC6 gene. Sac6p may allow GG-actin function in vivo by stabilizing the actin in bundles thereby helping maintain sufficient levels of an otherwise destabilized actin monomer
within the cell. |
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ISSN: | 0021-9258 1083-351X |
DOI: | 10.1074/jbc.274.50.35873 |