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1 June 2007 Analysis of the αB-crystallin domain responsible for inhibiting tubulin aggregation
Eri Ohto-Fujita, Yoshinobu Fujita, Yoriko Atomi
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The cytoskeleton has a unique property such that changes of conformation result in polymerization into a filamentous form. αB-Crystallin, a small heat shock protein (sHsp), has chaperone activities for various substrates, including proteins constituting the cytoskeleton, such as actin; intermediate filament; and tubulin. However, it is not clear whether the “α-crystallin domain” common to sHsps also has chaperone activity for the protein cytoskeleton. To investigate the possibility that the C-terminal α-crystallin domain of αB-crystallin has the aggregation-preventing ability for tubulin, we constructed an N-terminal domain deletion mutant of αB-crystallin. We characterized its structural properties and chaperone activities. Far-ultraviolet (UV) circular dichroism measurements showed that secondary structure in the α-crystallin domain of the deletion mutant is maintained. Ultracentrifuge analysis of molecular masses indicated that the deletion mutant formed smaller oligomers than did the full-length protein. Chaperone activity assays demonstrated that the N-terminal domain deletion mutant suppressed heat-induced aggregation of tubulin well. Comparison of chaperone activities for 2 other substrates (citrate synthase and alcohol dehydrogenase) showed that it was less effective in the suppression of their aggregation. These results show that αB-crystallin recognizes a variety of substrates and especially that α-crystallin domain binds free cytoskeletal proteins. We suggest that this feature would be advantageous in its functional role of holding or folding multiple proteins denatured simultaneously under stress conditions.

Eri Ohto-Fujita, Yoshinobu Fujita, and Yoriko Atomi "Analysis of the αB-crystallin domain responsible for inhibiting tubulin aggregation," Cell Stress & Chaperones 12(2), 163-171, (1 June 2007).
Received: 4 December 2006; Accepted: 1 February 2007; Published: 1 June 2007

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